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A 

TEXT   BOOK 


OF 


MECHANICAL  DRAWING 

PART   III. 

MACHINE    DRAWING, 

BY 

Gardner  C.  Anthony,  A.  M., 

PROFESSOR    OF    DRAWING   IN    TUFTS    COLLEGE  ; 

DEAN   OF   THE   BROMFIELD-PEARSON    SCHOOL  ; 

MEMBER    OF    AJVIERICAN    SOCIETY    OF    MECHANICAL    ENGINEERS. 


Copyright, 
By  Gardner  C.  Anthony, 
1893. 


Anno)( 
5U158i6S 


PREFACE. 


This  treatise  is  inteiuled  to  teach  the  practical  application  of  the  principles  of  projection  to 
the  illustration  of  machinery  ;  to  inform  the  student  concerning  many  of  the  exceptions  to  the 
laws  of  projection  ;  and  finally,  to  furnish  such  practical  examples  as  may  serve  for  problems  to 
the  student,  and  suggestions  to  the  draftsman.  It  aims  to  encourage  a  concise  graphic  expression 
in  the  colloquial  phrases  of  modern  mechanical  drawing,  instead  of  the  more  classic  language 
which  would  enforce  a  rigid  adherence  to  the  laws  of  projection,  and  the  customs  of  several 
centuries  of  architectural  draftsmen. 

The  examples  chosen  are  those  which,  being  faithfully  and  intelligibly  executed,  will  enable 
the  student  to  acquire  much  practical  information  on  the  subject  by  the  making  of  only  a  few 
drawings.  The  number  of  subjects  suitable  for  these  exercises  is  surprisingly  small ;  for  at  this 
period  of  the  student's  advancement,  it  is  the  art  of  graphic  expression  rather  than  that  of  drawing 
which  is  most  required,  and  this  cannot  be  attained  by  the  making  of  copies.  It  is,  indeed,  almost 
a  waste  of  time  to  copy  a  drawing,  since  proficiency  in  penciling  may  be  better  acquired  by  other 
means,  and  tracing  is  much  superior  as  an  exercise  in  inking.  The  difficulty  in  obtaining  suitable 
models  has,  however,  necessitated  much  of  this,  but  it  is  hoped  that  the  present  volume  may  assist 
in  obviating  the  trouble  by  supplying  such  problems  as  may  lead  the  student  to  observe  closely, 
think  accurately,  and  express  clearly.  The  subjects  chosen  for  the  exercises  are  such  as  have  been 
found  suitable  for  illustrating  most  of  the  principles  taught  as  well  as  the  practical  suggestions 
made  in  this  book. 


Iv 


PKEFACE. 


Much  care  has  been  exercised  in  the  making  and  figuring  of  these  drawings,  that  they  should 
be  complete  and  correct ;  but  tliat  this  should  be  realized  in  every  detail,  is  more  than  tiie  author's 
experience  would  lead  him  to  expect.  While  it  is  to  be  desired  that  the  one  great  lesson  of 
accuracy  should  be  emphasized  above  all  others,  it  is  also  to  be  remembered  that  draftsmen  are 
not  infallible,  and  it  is  the  minimum  rather  than  the  absence  of  mistakes  by  which  we  are  to  judge. 

As  this  book  is  tlie  advocate  of  no  special  systems  of  lining,  figuring,  lettering,  etc.,  the 
plates  will  be  found  to  represent  a  variety  of  types  in  drawing  which  may  at  some  time  serve  the 
draftsman  who  is  not  bound  to  special  methods  but  seeks  the  one  and  only  end  to  be  attained, 
namely,  the  art  of  using  all  available  instrumentalities  in  securing  a  terse,  accurate,  and  complete 
expression  of  mechanical  ideas. 

Gardner  C.  Anthony. 

Tufts  College,  Mass.,  Oct.  2,  1893. 


CONTENTS. 


CHAPTER  I. 

The  Representation  of  Bolts  and  Screws. 

screw  threads. 

U.  S.  Standard  Screw  Threads,  2  ;  Table  of  the  Strength  of  Screw  Threads,  4  ;  Table  of  Decimal 
Equivalents,  5  ;  Representation  of  V  Threads,  tj ;  Square  Threads,  (i ;   Buttress  Thread,  7. 

BOLTS    AND    SCREWS. 

U.  S.  Standard  Hexagonal  Head  and  Nut,  8;  Check-nuts  and  Washers,  10;   Square  Heads  and 
Nuts,  11;   Set-screws,  12;   Cap-screws,  13;    Round  Head  Screws,  13. 

CHAPTER  n. 

General  Rules  for  the  Making  of  Working  Drawings. 

Introduction,  14;  Classes  of  Drawings,  16;  Size  of  Sheet,  16;  Lay-out  of  the  Drawing,  17; 
Number  and  Arrangement  of  Views,  17  ;  Scale  to  be  Used,  18  ;  Method  of  Penciling  the 
Drawing,  19  ;  Method  of  Inking,  20  ;  Shade  Lines,  20  ;    Line  Shading,  21 ;  Title,  23. 


vi  CONTENTS. 

CHAPTER  III. 

SECTIONAL    VIEWS. 

Use  of  a  Section,  24  ;  vSection  Liners,  24  ;  Notation  for  Section  Lining,  25  ;   Dotted  Sections,  26  ; 
Colored  Sections,  28  ;  Choice  of  Cutting  Planes,  2^  ;  Broken  Sections,  32. 

FIGURING. 

Methods   considered,   32;  Rules  to  be    observed,  34;  Finding   Dimensions,  36;  Finished  Sur- 
faces, 36. 

TECHNICAL    SKETCHING. 

Value  and  Methods  of  Practice,  37  ;  Order  to  be  observed  in  the  making  of  a  Sketch,  38  ;  Practi- 
cal Observations,  39  ;   Sketch  Books,  40. 

CHAPTER  IV. 
Examples  for  Practice. 
Problem  1.     Assembled  Drawing  of  a  Locomotive  Parallel  Rod,  4L 

2.  Assembled  Drawing  of  a  Boiler  Check  Valve,  42. 

3.  Detailed  Drawing  of  a  Globe  Valve,  42. 

4.  Connecting  Rod,  42  ;   Method  of  determining  the  curves  of  intersection,  42  ;  Action 
of  Gib  and  Key,  44  ;   Assembled  Drawing  of  a  Connecting  Rod,  45. 

5.  Detailed  Drawing  of  a  Back  Rest,  46. 

6.  Assembled  Drawing  of  a  Screw  Polishing  Machine,  47. 

7.  Detailed  Drawing  of  a  Crosshead,  47. 

8.  Detailed  Drawing  of  the  Tail  Stock  of  a  17"  Lathe,  48. 

9.  Assembled  Drawing  of  the  Head  Stock  of  a  16"  Lathe,  48, 


CHAPTER   I. 
Bolts  and  Screws. 

The  representation  of  bolts,  nuts,  screws  and  screw-threads,  is  of  such  importance  that  a 
thorough  knowledge  of  their  proportions,  and  the  conventional  method  of  illustrating  them,  is  of 
the  first  consideration  to  the  machine  draftsman.  Printed  tables  of  the  dimensions  of  bolt-heads, 
nuts,  set-screws,  etc.,  are  usually  published  in  connection  with  treatises  on  machine  design,  but  it 
is  far  better  for  the  student  of  machine  drawing  to  fix  the  proportions  of  the  various  parts  in  his 
mind,  and  learn  to  judge  for  himself  of  their  comparative  value.  In  the  present  treatise,  only  the 
more  common  types  will  be  illustrated,  and  it  is  assumed  that  the  student  is  already  familiar  with 
the  theory  of  the  helix  and  its  application  to  the  various  forms  of  screw-threads,  as  well  as  the 
drawing  of  an  hexagonal  bolt-head  and  nut.*  In  the  study  of  the  following  pages  the  student  is 
recommended  to  so  master  each  type  that  he  may  rapidly  draw  or  sketch  the  bolt  or  screw  with  its 
proper  proportions,  having  only  the  diameter  of  the  thread  given. 


*  For  a  complete  t^c■ilti^^e  on  the  helix  and  its  applioation  to  the  drawing  nf  screw-threads,  together  wiih  the  construction  of  the 
hexagonal  holt-head  and  nut,  see  Part  II.  of  this  series. 


SCREW-THREADS. 


Scuew-Thkeads. 


The  form  of  screw-thread  commonly  used,  is  tliat  of  the  U.  S.  Standard,  also  known  as  the 
Franklin  Institute  Standard,  and  illustrated  by  Fig.  1.     The  proportion  of  pitch  to  diameter  is 

P=0.24i  D  4-0. 625-0. 175.  The  depth  of  the  thread  [S]  is  0.65  P. 
While  the  pitch  in  single  threaded  screws  is,  properly  speaking,  the 
distance  between  consecutive  threads,  the  term  is  often  applied  to  the 
number  of  threads  per  inch.  Thus  a  screw  having  eight  threads  to 
an  inch  is  frequently  spoken  of  as  8  pitch.  Although  this  is  obviously 
wrong,  yet  it  leads  to  no  confusion,  since  the  pitch,  and  the  number 
of  threads  per  inch,  are  reciprocals  of  each  other.  The  flattening  of 
the  thread,  as  indicated  in  the  figure,  is  for  the  purpose  of  preventing 
injury  to  the  thread  by  the  bruising  of  the  otherwise  sharp  V.  In 
the  following  table  the  proportions  of  this  thread  are  given  for  bolts 
from  i  to  4  inches  in  diameter.  To  this  is  also  added  the  tensile 
strength  of  the  screw  when  subjected  to  varying  stresses. 

Column  1  gives  the  outside  diameter  of  the  thread. 

Column  2  gives  the  number  of  threads  per  inch,  the  pitch  being 
the  reciprocal  of  this  number. 

Column  .3  gives  the  diameter  at  the  root,  or  bottom  of  thread. 
This  is  important  in  obtaining  the  diameter  of  the  tap  drill,  which  is 
approximately  given  in  the  next  column. 


Fig.  I     ^^ge  -^ 


LEFT  HAND 


RIGHT  HAND 


FiG.2 


SCREW-THREADS. 


i 


Column  4  gives  the  diameter  of  drill  to  be  used  for  any  given  diameter  of  thread  or  tap.  It 
will  be  noticed  that  these  sizes  are  a  trifle  larger  than  the  diameters  at  root  of  thread. 

Columns  5,  fi,  7  and  8  are  of  special  value  to  the  machine  designer,  but  are  introduced  here  to 
enable  the  student  to  obtain  some  appreciation  of  the  strength  of  the  V  thread.  The  weakest 
part  being  at  the  root,  its  strength  will  be  dependent  on  the  diameter  of  this  part  and  the  tensile 
strength  of  the  material.  In  the  case  of  a  screw  of  U  inch  diameter,  the  diameter  at  the  root  is  found 
in  column  3  to  be  1.065,  the  area  of  which  is  .78.  If  it  is  required  that  4000  lbs.  be  the  strain 
to  which  every  square  inch  is  subjected,  then  will  the  thread  sustain  .78  times  4000  lbs.  which 
is  3120  as  given  in  column  5.  In  this  manner  the  table  is  constructed  for  four,  five,  six  and 
seven  thousand  pounds  tensile  strength.  A  valuable  application  of  this  table  is  in  determming 
the  size  of  a  screw,  having  given  the  total  load  to  be  sustained  and  the  permissible  strain  per 
square  inch.  Suppose  it  is  required  to  obtain  the  diameter  of  a  bolt  sufficient  to  overcome  a  re- 
sistance of  32000  lbs.  and  to  be  strained  to  only  4000  lbs.  per  square  inch.  In  column  5  is 
found  the  number  33000,  which  is  the  nearest  to  the  required  amount.  Against  this  number,  in 
column  1,  is  seen  SJ,  which  is  the  necessary  diameter  of  screw.  If,  however,  the  allowable  strain 
per  square  inch  had  been  7000  lbs.  a  screw  of  2f  inch  diameter  could  have  been  used. 

In  connection  with  this  table,  one  of  decimal  equivalents  is  also  published.  The  student 
should  not  be  dependent  on  this  for  the  equivalents  of  eighths  and  sixteenths  of  an  inch,  as  they 
may  be  so  easily  memorized  and  are  of  such  frequent  use. 


SCREW-THREADS . 

U.  S.  STANDARD  THKEAD. 


Diame- 
ter  of 
Scifw. 

Threads 

per 

luch. 

Diameter 

at  root    of 

Thread. 

Diame- 
ter of 
Tap  Drill 

Tensile     |    Tensile 
Strength  at;Strcngth  at 
4000  lljs.per  60OO  Ihs.per 

sq.  Inch.        sq.  Inch. 

Tensile    |    Tensile 

•Strength  at  Strength  at 

eoooibs.  perTOOOlbs.per 

sq.  Inch.       sq.  Inch. 

1 

4 

20 

.185 

A 

107 

134 

161 

187 

^ 

18 

.240 

L 

181 

226 

271 

316 

s 

16 

.294 

A 

271 

339 

407 

475 

-;v 

14 

.344 

23 

371 

465 

558 

650 

i 

13 

.400 

Yi 

500 

625 

750 

875 

A 

12 

.454 

15. 

647 

809 

971 

1133 

a 

11 

.507 

1^' 

784 

980 

1176 

1372 

3 

10 

.620 

R 

1200 

1500 

1800 

2100 

I. 
8 

9 

.731 

4 

1680 

2100 

2520 

2940 

1 

8 

.8157 

li 

2200 

2750 

3300 

3850 

u 

7 

.940 

2760 

3450 

4140 

4830 

ll 

7 

1.065 

1,^- 

3120 

3900 

4680 

5460 

IS 

6 

1.160 

lA 

4240 

5300 

6360 

7420 

u 

6 

1.284 

13^2 

5120 

6100 

7680 

8960 

1§ 

5\ 

1.389 

isi 

eiL'O 

7650 

9180 

10710 

H 

5 

1.491 

n 

7040 

8800 

10560 

12320 

H 

5 

1.616 

n 

8120 

10150 

12180 

14210 

2 

4i 

1.712 

^ 

9200 

11500 

13800 

16100 

2i 

4i 

1.962 

2 

12480 

15600 

18720 

21840 

2J- 

4 

2.176 

2A 

14800 

18500 

22200 

2.5900 

2iJ 

4 

2.426 

2.^6 

18400 

23000 

27600 

32200 

3 

3!> 

2.629 

2j!, 

217(;u 

27200 

32K4U 

38080 

3V 

31 

2.879 

2U 

26400 

33000 

39600 

46200 

Sk 

3} 

3.100 

H' 

30160 

37700 

45240 

52780 

3J 

3 

3.317 

Hh 

34400 
39600 

43000 

51600 

60200 

4 

3 

3.567 

49500 

594U0 

69300 

SCBEW-THRKADS . 


DECIMAL  EQUIVALENTS. 


Fraction. 

Decimal. 

Fraction. 

Decimal. 

Fraction. 

Decimal. 

Fraction. 

Decimal. 

tV 

.015625 

.03125 

.046875 

.265625 

.28125 

.296875 

If 

.515625 

.53125 

.546875 

u 

2  a 
SS 

u 

.765625 

.78125 

.796875 

.0625 

5 

.3125 

tV 

.5635 

H 

.8125 

8 

.078125 

.09375 

.109375 

11 

II 

.328125 

.34375 

.359375 

.578125 

.59375 

.609375 

.8281<;5 

.84375 

.859375 

.125 

3 
S 

.375 

5 

8 

.625 

i 

.875 

.140625 

.15625 

.171876 

ft 

u 

.390625 

.40625 

.421875 

U 

.640625 

.65625 

.671875 

ii 
II 

.890625 

.90625 

.921875 

A 

.J  875 

A 

.4375 

H 

.6875 

n 

.9375 

.203125 

.21875 

.234375 

.453125 

.46875 
.484375 

II 

.703125 

.71875 

.734375 

.953125 

.96875 

.984375 

1 

4 

.25 

'2 

.5 

3 

4 

.75 

1 

FiG.3 


SCREW-THREADS. 

Representation  of  V  Threads. — It  is  very  rarely  that  a 
thread  would  be  shown  as  in  Fig.  1  and  seldom  as  in  Fig.  2,  since 
the  labor  of  drawing  the  V  is  very  considerable.  The  best  conventional 
method  of  representing  the  V  thread  is  shown  by  Fig.  3,  although  that 
of  Fig.  4  is  much  used.  The  objection  to  the  latter  form  is  in  tlie 
greater  length  of  the  heavy  lines  which  obscures  more  of  the  drawing, 
often  making  too  little  space  for  the  figures.  It  is  rarely  necessary  to 
draw  the  exact  number  of  threads  per  inch,  required  by  the  table;  in- 
deed the  representation  is  usually  clearer  when  a  less  number  is  used, 
and  the  drawing  of  unnecessary  lines  is  also  saved.  If  it  is  of  importance 
to  specify  tiie  pitch,  it  is  best  done  by  Roman  numerals,  indicating  the 
number  per  inch.  A  double  thread  is  shown  by  Fig.  5,  for  the  pur- 
pose of  calling  attention  to  the  difference  between  it  and  the  single 
thread.  The  character  of  the  double  thread  is  better  shown  by  Fig.  6. 
Fig.  4  in  the  case  of  a  dotted  thread,  economy  in  the  use  of  lines  is  of  still 

greater  importance,  and  the  V  alone  is  often  shown  as  illustrated  by 
Fig.  17  or  in  a  practical  drawing  by  the  cross-head  pin,  and  gib  set- 
screws  of  Plate  10. 

Square  Threads. — In  Fig.  7  three  forms  of  the  square  thread  are 
represented.  To  the  right  is  the  section  showing  the  proportion  of  pitch 
to  depth  of  thread.  In  the  middle  is  drawn  the  more  correct  conven- 
tional representation,  and  on  the  left  is  the  simple  form  commonly  used. 
In  the  latter  it  will  be  observed  that  the  inner  helix  is  omitted  and  in 


Fig.  5 


SCRE\V-TH  HEADS. 

this  type  of  screw  it  is  also  better  to  draw  the  exact  number  of  threads 
required,  except  the  scale  be  small  or  the  pitch  very  fine. 

Buttress  Thread.— Fig.  8  illustrates  a  third  type  which  is 
sometimes  known  as  a  ratchet  thread.  It  is  used  for  imparting  motion 
but  only  in  cases  where  the  strain  is  in  one  direction,  as  in  a  screw  jack. 
By  this  means  the  friction  is  reduced,  while  the  strength  of  the  V  thread 
is  maintained.  There  is  no  standard  for  this  thread,  but  the  usual  form 
and  proportion  is  that  shown  by  the  figure. 

Bolts   and  Screws. 

Save  for  the  hexagonal  bolt-head,  there  is  no  generally  accepted 
standard  for  the  heads  of  bolts  and  screws.  For  the  draftsman  it  is 
essential  however,  that  some  system  be  used  in  the  illustration  of  forms 
which  occur  so  frequently  as  do  these.  The  time  required  to  properly 
design  the  head  of  a  bolt,  set-screw,  or  other  fastening  device,  is  very 
considerable,  and  to  have  done  it  once  should  suflice.  When  a  definite 
form  of  head  is  required  it  should  only  be  necessary  to  produce  the 
same  according  to  certain  proportions  already  fixed,  and  obtainable 
either  from  a  ready  reference  table  or,  better  still,  from  memory.  As  it 
is  generally  unnecessary  to  give  all  the  dimensions  of  the  head  or  nut  on 
the  drawing,  it  is  immaterial  whether  the  representation  conforms  exactly 
to  the  finished  size  or  not.     It  is  therefore  a  useless  delay  for  the  drafts- 


OOUBLE    THREAD 


-c-P-A-F 


Fig.  6 


Fig.  8 


BOLTS    AND    SCREWS. 


r^^^3^^^«Tsrtv 


man  to  spend  any  more  than  time  enough  to  produce  the  desired  type  of 
head  according  to  his  standard.  The  following  proportions  are  suggested 
from  standards  already  in  use  by  many  shops. 

U.  S.  Standard  Hexagonal  Head  and  Nut. — Two  types  of 
head  and  nut  are  illustrated,  the  rounded  or  spherical  Figures  9,  10, 
11,  and  chamfered  or  conical  Figures  13,  13,  1-1.  In  general 
the  chamfered  head  is  used  for  sketching,  for  rough  work  and  when- 
ever a  special  finish  is  not  required.  The  rounded  head,  which  pre- 
sents a  more  finished  appearance,  is  used  almost  exclusively  for  the  heads 
and  nuts  of  bolts  for  finished  machinery.  Three  dimensions  only  are 
fixed  by  the  Government  standard,  viz.,  the  distance  across  flats,  or  short 
diameter,  commonly  marked  H  and  equal  to  one  and  one-half  times  the 
diameter  of  the  bolt,  plus  one-eighth  of  an  inch.  Second,  the  thickness  of 
the  head,  equal  to  one-half  the  short  diameter.  Third,  the  thickness  of 
nut,  which  is  equal  to  the  diameter  of  the  bolt. 

In  the  following  suggestions  for  the  drawing  of  hexagonal  heads 
it  should  be  remembered  that  the  rounded  type  is  a  sphere  cut  by  six 
planes  parallel  to  the  axis,  while  the  chamfered  head  may  be  considered  as 
a  cone  similarly   cut. 

Fig.  1). — Having  determined  H  or  the  short  diameter  and  drawn 
the  edges,  lay  off  the  thickness  of  head  and  describe  the  top  with  a  radius 
of  twice  the  diameter  of  bolt.  To  obtain  the  arc  ABC,  determine  point 
B  which  is  equal  in    hight  to  K,  and  through  it  describe  the  required  arc 


BOLTS    AND    SCREWS. 


with  radius  equal  to  M  N,  using  care  to  have  C  and  A  of  same  hight. 
The  fine  dotted  lines  show  the  precise  method  of  finding  these  points  by 
obtaining  the  long  diameter. 

Fig".  10. — Figure  the  short  diameter  and  obtain  the  long  diameter 
geometrically  as  shown  by  the  dotted  lines.  [In  small  bolts,  or  drawings 
to  small  scale  the  long  diameter  may  be  made  equal  to  2  D.]  The  edge 
SL  is  equidistant  from  VW  and  the  center  line,  and  equal  to  V  AV  in 
lensth.  Throudi  S  describe  arc  O  R  S  concentric  with  curvature  of  top. 
Tiu-ough  S  and  V  describe  arc  S  E  V  with  radius  equal  to  L  W. 

Fig.  11. — This  differs  from  the  preceeding  only  in  that  the  thick- 
ness is  equal  to  the  diameter  of  the  bolt.  Observe  also  that  the  curvature 
of  the  top  begins  at  G  instead  of  on  the  center  line. 

Figures  13,  13,  and  14-. — In  drawing  the  chamfered  head  or 
nut  across  corners,  as  in  Figures  12  and  14,  describe  ABC  tangent 
to  top  with  radius  equal  to  diameter  of  bolt.  From  the  same  center 
describe  arc  E  F,  point  F  being  equal  in  hight  to  C. 

Heads  and  nuts  drawn  in  connection  with  the  parts  which  they  unite 
should  in  general  be  shown  across  corners.  This  will  prevent  errors  in 
the  allowance  to  be  made  for  hubs,  washers,  etc.,  as  it  gives  the  maximum 
space  required  for  the  head.  The  necessity  for  observing  this  is  at  times 
80  great  that  the  bolt  is  required  to  be  drawn  across  corners  in  all  views 
in  which  it  may  appear.  In  sketcliing  bolts  and  in  the  making  of  bolt 
lists  it  is  better  to  represent  them  across  flats,  as  they  are  both  more  easily 
drawn^and  figured. 


Fig.  1 2 


Fig.  13 


Fig.  14 


10 


BOLTS    ANJ)    SCREWS. 


Fig.  15  illustrates  a  bolt  with  check-nuts  and  washers.  It  is  a  common  practice  to  make 
both  nuts  of  the  same  thickness  and  equal  to  three-quarters  of  the  diameter  of  the  bolt.  The 
more  proper  form,  however,  is  to  make  the  thickness  of  the  nut  sustaining  the  load  equal  to  the 
diameter  of  bolt.  Observe  also  that  the  outer  nut  is  chamfered  on  both  faces.  This  might  be 
done  in  all  cases,  but  polished  parts  united  by  bolts  having  heads  and  nuts  so  chamfered,   are  not 


-^ 


^ 


hi 

T 


L    LENGTH      

F,G.I5  '  «^'<^16 

so  easily  wiped,  since  the  oil  and  dust  is  likely  to  lodge  under  the  corners.  The  necessity  for 
chamfering  the  outer  faces  is  very  great,  as  otherwise  the  sharp  corners  would  cause  difficulty  in 
handling  and  soon  become  marred. 

When  a  tapped  hole  is  extended  for  some  length  beyond  the  end  of  the  screw  or  bolt,  as  in 
Fig.  16,  it  is  better  not  to  draw  the  threads  in  this  portion  if  the  piece  tapped  be  in  section.  But 
if  a  tapped  hole  be  shown  in  a  section  then  the  threads  may  be  shown  as  at  A,  Fig.  17.  Dotted 
representations  of  the  same  thread  are  shown  by  B  and  C. 


BOLTS    AND    SCREWS. 


11 


The  end  view  of  a  tapped  hole  is  often  illustrated  by  the  drawing  of  two  circles  in  order  to 
distinguish  it  from  a  drilled  hole.  In  such  cases  the  outer  circle  is  made  equal  to  the  diameter  of 
the  thread. 

The  length  of  a  bolt  is  measured  from  the  underside  of  the  head  to  the  end,  unless  the  end  be 


Fig  18 

part  only,  as  in  Fig.  18.       The  length  of 


rounded,  in  which  case  it  is  usual  to  figure  the  straight 
the  thread  must  of  course  be  figured  from  the  end. 

Square  Headed  Bolts,  Nuts  and  Screws. 
usually  observed  for  the  square  also,  save  in  the  radius 
to  be  two  and  one-half  diameters. 

Fig-.  18 The  arc  A  B  C  is  concentric  with  the  top  and  is  described  through  the  point  B 

which  is  equal  in  hight  to  E,     In  drawing  the  head  or 


-The  proportions  for  hexagonal  heads  are 
for  the  curvature  of  the  top,  which  is  better 


nut  across  corners  the  geometrical  method 


12 


BOLTS    AND   SCREWS. 


may  be  used  as  shown,  remembering  that  F  G  is  equal  to  half  the  short  diameter,  and  F  K  half 
the  long  diameter.  Or  the  long  diameter  may  be  made  equal  to  one  and  one-half  the  short 
diameter  in  small  bolts,  or  where  accurate  work  is  not  required. 


LUgJ  1 


Fig.  20 


FiG.21 


"f 

(M 

1 

1 

b 

Fig.  22 


Set-screw,  Fig.  19. — The  construction  of  this  will  be  apparent  from  the  figure  on  which 
the  proportions  are  given.  Of  course  it  is  unnecessary  to  draw  the  top  view  as  the  distance  marked 
A  can  be  estimated  by  the  eye.     The  radius  for  the  point  of  a  set-screw  should  be  four  diameters. 

Fig'uve.s  yO,  31  aii<l  'i'i  represent  three  other  types  of  screws  having  square  heads.  In  the 
gib-screw  Fig.  *-il,  the  [troportion  adopted  for  the  short  diameter  is  also  excellent  for  the  squaring 
of  the  end  of  any  rod,  as  must  frequently  be  done  for  a  box  wrench,   Fig.  33. 


BOLTS    AND   SCREWS. 


13 


Cajj-screw,  Fig.  33. — This  is  an  excellent  type  for  many  purposes  where  a  small  diameter 
of  head  is  required.  The  extra  length  of  the  head  makes  it  especially  suitable  for  places  where 
frequent  adjustment  is  needed. 

Hound  Head  Screws,  Figures  33  and  34. — These  differ  only  in  depth  of  head  and 


<HD]- 


f 


Fig'.  23 


— »— I— ,-i _l       X 

hA+o-J         S 


Fig.  24- 


FiG.25 


finish  of  end.  The  type  of  Fig.  35  being  better  adapted  for  countersunk  work,  since  a  variation 
in  the  depth  of  the  hole  will  not  effect  the  appearance  of  the  fit  as  would  be  the  case  in  that  of 
Fig.  34.  In  representing  the  end  view  of  a  slotted  head,  always  draw  the  lines  of  the  slot  at  an 
anfle  of  45  decrees,  thereby  making  greater  contrast  with  other  lines  of  the  drawing  and  thus  pre- 


venting confusion. 


The  figured  length  of  these  screws  should  always  include  the  head. 


CHAPTER  II. 

General  Rdles  for  the  Making  of  a  Working  Drawing. 

introduction. 

Drawing  is  a  graphic  language,  and  may  best  be  studied  by  subjecting  its  use  to  laws  similar 
to  those  governing  other  languages.  Like  others,  it  has  its  orthography,  grammar,  and  litera- 
ture. Its  orthography,  consisting  of  the  various  types  of  lines,  its  grammar  being  the  art  of  repre- 
senting objects  upon  planes,  and  known  as  orthographic  projection  ;  and  finally  its  literature,  con- 
sisting of  the  practical  application  of  these  principles  to  the  drawings  which  we  are  required  to 
read  and  write.  But  in  this,  as  in  all  languages,  we  cannot  be  governed  entirely  by  laws,  but 
must  familiarize  ourselves  with  the  idioms  and  conventional  methods  of  our  day,  remembering 
always  that  it  is  simply  a  medium  for  the  expression  of  our  thoughts. 

A  drawing  fulfills  its  object  only  when  it  clearly  sets  forth  the  ideas  to  be  expressed,  and  in 
nowise  misleads  the  reader  to  whom  it  is  especially  addressed.  If  it  fails  to  do  this,  it  is  a  poor 
drawing,  regardless  of  the  fact  that  it  may  conform  to  all  established  laws  and  be  executed  with 
the  greatest  precision  and  elegance.  A  drawing  should  be  regarded  as  a  business  letter  to  the 
mechanic,  and  must  first  of  all  be  brief,  having  as  few  lines  and  figures  as  possible.  It  must 
completely  express  the  idea,  omitting  no  lines  or  views  necessery  to  attain  this  end.  It  must 
contain  nothing  that  may  mislead,  even  though  it  be  to  violate  the  laws  of  projection.  The  char- 
acter of  the  drawing  must  be  determined  by  the  use  to  which  it  is  put.     If  a  free-hand  sketch  is 


INTRODUCTION.  15 

sufficiently  comprehensive,  and  will  in  every  way  serve  the  purpose  of  the  finished  drawing,  it  is  a 
waste  of  labor  to  make  the  latter.  On  the  other  hand,  no  pains  should  be  spared  in  the  exe- 
cution of  the  drawing  if  it  will  better  express  the  designer's  conception  of  the  mechanism.  No 
portion  of  such  work  should  be  carelessly  done,  even  in  the  so-called  off-hand  sketch, 
or  drawino-.  A  sketch  may  consist  of  few  lines  and  be  comparatively  rude,  but  it  must  not  be 
thouo-htlessly  executed.  Again,  the  draftsman  must  consider  the  class  of  mechanics  to  whom  his 
drawing  is  addressed.  He  should  anticipate  their  wants,  and  to  a  certain  extent,  guard  against 
mistakes  which  may  arise  from  their  ignorance.  Experience  alone  will  make  a  man  proficient  in 
the  use  of  this  graphic  language,  but  a  knowledge  of  the  laws  governing  it  will  greatly  facilitate 
its  acquisition. 

The  development  of  machine  drawing,  during  the  last  few  years,  has  resulted  in  the  introduc- 
tion of  many  methods  and  technicalities  which  were  not  formerly  required.  The  technical  part  of 
architectural  drawing  has  never  necessitated  such  rigid  conformity  to  laws  concerning  the  arrange- 
ment of  views,  methods  of  sectioning,  figuring,  and  other  details,  and  it  is  for  this  reason  that  many 
apparent  innovations  have  necessarily  been  made  upon  the  old  established  systems  of  drawing.  No 
one  chano-e  has  caused  more  discussion  than  the  rigid  adherence  to  the  representation  of  all  objects 
in  what  is  known  as  the  third  angle  of  projection,  that  is,  the  placing  of  the  top  view  on  the  top  of 
the  sheet,  the  view  of  the  right-hand  on  the  right-hand  of  the  sheet,  etc.  ;  in  short,  placing  the 
view  nearest  to  the  face  which  it  represents.  But  this  has  now  passed  the  stage  when  the  advan- 
tages to  be  derived  by  this  method  may  be  questioned,  and  to-day,  no  well  conducted  draughting 
room  will  permit  any  other  system  to  be  used. 

This  treatise  presupposes  a  knowledge  of  the  use  of  instruments  and  the  theory  of  orthographic 
projection.     Its  aim  is  to  teach  the  more  concise  methods  of  graphically  expressing  mechanical  ideas. 


]6  CLASSES    OF   DRAWINGS. 

Classes  of  Drsiwiug'S. — The  different  types  of  drawing  required  for  siiop  uses  are  as 
follows  : 

The  General  or  Assembled  Drawing. — This  consists  of  a  representation  of  the  complete 
machine  with  all  of  its  parts  sustaining  their  proper  relations  to  eacli  other.  This  drawing  may 
contain  information  suitable  only  for  assembling  the  macliine,  and  illustrating  tiie  general  design, 
or  it  may  also  include  some  or  all  of  the  details  of  the  machine.  The  drawing  of  the  Tail  Stock, 
Plate  11,  is  of  this  type. 

Detail  Drawings. — These  illustrate  each  piece  separately,  with  all  of  the  information  neces- 
sary for  its  construction.  This  type  is  shown  by  Plates  7  and  8.  It  is  customary  to  devote  one 
or  more  sheets  to  forgings,  and  others  to  castings,  or  when  the  parts  are  few  in  number  they  may 
be  placed  on  a  single  sheet. 

Bolt  Drawings. — Where  a  great  variety  of  bolts  is  used  on  a  machine,  a  special  drawing 
of  them  is  required,  or  a  Bolt  List  may  be  prepared  which  shall  enumerate  the  sizes,  type  and 
number  of  each. 

Motion  Diagram. — This  type  would  be  used  only  in  complicated  machinery  comprising  a 
number  of  mechanical  motions  more  or  less  complicated.  Sucli  a  drawing  would  instruct  concern- 
ing the  relation  of  important  centers,  direction  of  motiun,  relative  velocity  of  shafts,  etc. 

The  size  of  paper  used  for  the  drawing  is  usually  determined  by  certain  fixed  standards 
peculiar  to  each  shop  and  largely  dependent  on  the  uses  for  which  the  drawings  are  designed.  For 
the  problems  of  this  book,  the  sizes  of  10x14  and  14x20  inches  are  recommended,  but  nearly  all 
of  the  work  may  be  drawn  on  the  smaller  size.  These  dimensions  are  for  the  margin  line,  the 
size  of  the  paper  being  as  much  greater  as  may  seem  suitable.  From  one-half  to  one  inch  margin 
is  sufficient. 


LAY-ODT    OF   THE    DRAWING.  17 

The  Lay-out  of  the  Drawing. — Having  put  down  the  paper  and  ruled  the  margin,  obtain 
a  "lay-out"  of  the  sheet.  This  consists  in  the  making  of  a  rude  sketch  of  the  various  parts  and 
views  to  be  put  on  the  drawing,  so  that  ample  room  shall  be  provided  for  each  piece  and  the  whole 
be  symmetrically  arranged.  This  operation  is  usually  neglected  by  students,  and  inevitably  leads 
to  trouble  and  the  loss  of  much  more  time  than  would  be  required  for  the  preliminary  sketch. 
Where  a  number  of  details  are  to  be  put  on  a  drawing,  as  shown  on  Plate  8,  provision  must  be 
made  for  the  proper  marking  of  each  piece  as  well  as  the  necessary  figure  lines.  If  the  detail  is  of 
a  small  piece,  like  some  of  the  screws  on  this  plate,  much  more  space  should  be  allowed  than 
would  be  sufficient  for  the  piece  itself,  as  the  title  alone  may  require  more  space  than  the  drawing 
of  the  piece.  If  provision  for  each  part,  and  the  necessary  views,  be  not  made  before  the  drawing 
is  begun,  the  draftsman  may  discover,  when  it  is  too  late  to  rectify  the  mistake,  that  some  piece 
has  been  omitted,  thus  requiring  an  entire  sheet  to  be  devoted  to  this  piece,  or  the  re-drawing  of 
the  whole. 

Nnniber  and  Arrangfenient  of  Views. — This  discussion  of  the  arrangement  of  a 
sheet  leads  to  the  consideration  of  the  number  and  arrangement  of  views.  The  only  rule  for 
guidance  in  this  matter  is  to  draw  as  few  views  as  shall  be  consistent  with  the  interpretation  of  the 
idea,  but  enough  to  accomplish  this  fully.  In  the  valve  drawing,  Plate  3,  one  view  would  suffice 
for  the  complete  representation  of  the  object,  two  being  shown  here  to  simplify  the  problem  for  the 
student.      In  Plate  9,  two  views  are  barely  sufficient  for  the  ready  reading  of  the  drawing. 

The  views  should  bear  such  relation  to  each  other  as  that  already  prescribed  for  the  orthographic 
projection  of  objects  in  the  third  angle,  the  top  view  on  the  top  of  the  sheet,  the  view  of  the  right 
side  of  the  object  to  the  right  of  the  sheet,  etc.  A  good  rule  to  observe  for  attaining  this  end  is 
to  place  the  view  nearest  the  face  represented. 


18  SCALE    TO    BE    USED. 

In  the  making  of  .a  general  drawing  which  is  to  be  used  for  assembling  only,  omit  as  much 
detail  as  possible. 

Parts  which  may  be  well  represented  on  one  view  need  not  necessarily  appear  on  the  other 
views. 

Draw  nothing  that  may  mislead  or  that  does  not  assist  in  conveying  the  idea  to  be  expressed. 

When  a  written  note  will  serve  the  making  of  a  second  view,  do  not  hesitate  to  insert  it. 

In  general,  show  mechanism  in  its  working  position,  with  the  parts  sustaining  their  proper 
relations  to  each  other.  Thus  in  drawing  a  valve,  let  it  be  either  wide  open  or  closed.  In  showing 
a  steam  cylinder,  draw  the  piston  at  extreme  end  of  stroke,  and  the  valve  in  its  proper  relation  to 
the  piston. 

f////////////////////////////////////W/W'fW/Wf 


\\\\\\\\\\\\\\\\\W\\\^\\\\\\WvA\v\\^^^ 

Scale  to  be  Used. — The  scale  of  a  drawing  is  usually  dependent  on  the  size  of  sheet  and 
number  of  views.  These  being  determined,  use  the  largest  possible  scale.  Those  commonly  em- 
ployed are  :  Full  size,  Half  size.  Quarter  size  (3  inches=l  foot),  Eighth  size  (li  inche8=l  foot). 
The  scale  of  2  inches  =1  foot  is  much  used  in  locomotive  practice,  but  is  not  to  be  commended  for 
general  use  as  it  requires  special  division  of  the  scale. 

The  most  convenient  form  of  scale,  and  indeed  the  only  kind  that  the  author  can  recommend, 
is  the  flat  boxwood  scale  with  white  edge,  graduated  alike  on  both  edges.     Such  a  scale,  divided 


tENCILtNG   THE    DRAWING.  19 

into  sixteenths  for  its  entire  length,  and  thirty  seconds  for  the  first  inch  from  either  end,  is  suitahle 
for  use  on  the  Full,  Half  Quarter,  and  Eighth  size  drawings.  In  using  this  form  of  scale  for  a 
Half  size  drawing  the  reduction  is  easily  made,  since  all  dimensions  are  halved,  but  in  the  Quarter 
size,  a  difficulty  would  be  experienced  if  it  were  necessary  to  figure  the  fourth  part  of  all  dimensions 
before  laying  them  off.  This,  however,  may  be  obviated  in  the  following  manner  which  is  best 
illustrated  by  an  example.  Suppose  it  is  required  to  lay  off  19^  inches.  Remembering  that  one- 
quarter  of  an  inch  of  the  scale  represents  one  inch,  lay  off  as  many  quarters  as  there  are  inches 
required,  and  since  one-thirty-second  of  the  scale  represents  one-eighth  of  an  inch,  add  seven  of 
these  divisions  to  the  amount  already  measured.  In  short,  it  is  using  the  scale  as  though  each 
quarter  of  an  inch  was  marked  as  an  inch  in  the  same  manner  as  the  regular  quarter  scale  division. 
The  same  method  may  also  be  applied  to  the  eighth  scale.  But  if  the  ordinary  graduation  for  a 
quarter  or  eighth  size  be  desired,  let  it  be  on  a  scale  separated  from  all  other  graduations.  The 
ordinary  triangular  scale  with  its  numerous  graduations  and  awkward  shape  is  probably  the  worst 
form  of  scale  that  was  ever  devised,  especially  when  made  of  steel.  The  draftsman  who  has  any 
consideration  for  his  eyes  will  never  use  a  steel  scale  for  general  work. 

Method  of  penciling  the  drawing. — Locate  main  center  lines  according  to  lay-out 
sketch,  and  begin  to  draw  the  view  which  best  illustrates  the  object. 

Next  locate  leading  lines  and  surfaces.  If  the  subject  be  the  head-stock  of  a  lathe,  draw  the 
spindle,  fix  the  position  of  bearings  and  pulleys,  and  then  proceed  with  the  drawing  of  the  casting. 
If  a  stub-end  drawing  is  required,  as  in  Plate  5,  lay  oflTthe  dimensions  for  the  principal  lines  in 
much  the  same  order  as  indicated  by  the  letters  alphabetically  arranged.  First,  the  diameter  and 
length  of  the  box  A  and  B.  Then  the  position  of  end  of  rod  C,  depth  of  rod  G,  keys  and 
key  ways,  intersections,  etc. 


20  INKING. 

Omit  minor  details  until  all  else  is  finished.  If  a  bolt,  key,  spring  or  any  other  such  detail 
occurs,  its  position  may  be  marked,  but  the  drawing  of  it  should  be  deferred  until  all  else  is  proved 
correct. 

Do  not  complete  the  views  separately,  but  having  one  well  begun,  commence  the  drawing  of 
others.  In  this  manner  errors  are  more  readily  detected,  the  drawing  of  each  view  becoming  a 
check  to  the  others. 

Ink  no  part  of  a  drawing  until  the  penciling  be  complete.  In  a  complicated  drawing,  students 
are  often  tempted  to  ink  a  view  or  part  of  a  view,  which  they  feel  confident  to  be  correct,  and 
before  quite  finishing  the  drawing.     This  should  never  be  done. 

Method  of  Inking. — The  order  to  be  observed  in  the  finishing  of  a  drawing  is  as  follows  : 
Ink  all  circles  and  circular  arcs,  beginning  with  the  smallest.  This  includes  all  fillets  and  round- 
ino-  of  edsee.  If  shade  lines  are  used,  shade  each  arc  at  the  time  of  inking  it.  It  will  be  observed 
then  that  the  width  for  both  fine  and  heavy  lines  is  determined  by  the  shading  of  the  first  circular 
arc.  Do  not  use  too  fine  a  line,  remembering  always  that  the  drawing  must  be  distinct  even  after 
much  use  and  possible  abuse.     Next,  ink  all  other  curved  lines,  such  as  lines  of  intersection,  etc. 

Finally,  ink  all  fine  lines,  both  full  and  dotted  ;  and  then  the  heavy  or  shade  lines. 

Section  lines  should  not  be  drawn  until  the  figuring  is  completed. 

Shade  Lines. — By  some  draftsmen  the  use  of  shade  lines  is  condemned  while  others  con- 
sider a  drawing  as  incomplete  without  them.  Both  err  by  adopting  either  system  to  the  exclusion 
of  the  other,  for  while  shade  lines  may  be  useless  on  many  drawings,  there  are  others  which  would 
be  incomplete  without  them.  The  draftsman  must  decide  the  matter  for  each  drawing  which  he 
makes,  always  using  them  when  they  may  assist  in  the  reading  of  the  drawing,  but  otherwise 
omitting  them. 


LINE    SHADING. 


21 


The  only  practical  direction  that  may  be  given  for  the  method  of  using  them  is  to  shade  the 
right-hand  and  lower  edges  of  all  surfaces,  remembering  that  in  the  case  of  contact  between  sur- 
faces, the  line  represents  the  surface  nearest  the  observer.  Where  the  surfaces  are  flush,  as  is  the 
case  between  the  stub-end  of  the  connecting  rod  and  the  strap,  Plate  5,  the  line  must  be  fine. 
Never  shade  the  intersecting  lines  between  visible  surfaces  of  the  same  piece,  as  illustrated  by  the 
division  line  of  the  faces  of  a  bolt-head.  Shade  the  lower  right-hand  quadrant  of  outside  circles 
and  the  upper  left-hand  quadrant  of  inside  circles.  Do  not  permit  the  shade  line  to  encroach  on 
the  surface  which  it  bounds. 

Cylindrical  surfaces  are  sometimes  illustrated  by  fine  lines  only,  when  shade  lines  are  used 
on  other  surfaces.  This  method  is  especially  adapted  to  the  illustration  of  a  complex  piece  having 
an  insufficient  number  of  views  or  lacking  in  detail.    Plate  9  will  be  found  to  illustrate  this  method. 

Line  Sluiding.— It  is  often  necessary  to  express  the  character  of  a  surface  more  clearly 
than  would  be  done  by  the  simple  outline  or  by  the  use  of  shade  lines.  This  is  ordinarily  accom- 
plished by  the  use  of  line  shading.  Plate  16  illustrates  the  method  of  shading  the  more  common 
surfaces.  In  studying  these  methods  and  in  applying  them  to  the  practical  drawing  it  should  be 
observed  that  the  best  effects  are  frequently  produced  by  the  fewest  lines,  and  the  more  we  are 
able  to  reduce  the  number  of  lines  of  all  types,  the  better  the  drawing.  By  the  system  here 
shown,  much  of  the  cylindrical  and  conical  shading  might  to  advantage  be  done  by  a  section  liner* 
which  in  the  case  of  large  surfaces  would  insure  more  regular  work.  In  shading  large  cylindrical 
surfaces  such  as  Fig.  1,  Plate  16,  use  only  fine  lines  for  the  upper  portion.  Increase  the  space 
between  the  lines  quite  rapidly  and  stop  at  about  one-half  of  the  radius  from  the  top.  The  shad- 
ing of  the  lower  part  may  be  begun  at  a  distance  of  about  one-quarter  of  the  radius  from  the  center. 


*  For  a  descriptiou  of  this  instrument  and  tlio  method  of  operating  it  see  page  24. 


22  LINE    SHADING. 

These  lines  may  be  spaced  equally,  although  the  appearance  is  somewhat  improved  by  increasing 
tiie  space  for  the  first  two  or  three  lines.  The  cylindrical  effect  is  produced  by  increasing  the 
width  of  the  lines  until  near  the  bottom,  when  they  are  slightly  decreased  in  width,  but  this  latter 
is  not  necessary  save  in  cylinders  of  large  diameter.  Fig.  4  illustrates  the  section  of  a  cylinder, 
which  being  a  concave  surface,  necessitates  the  drawing  of  the  darker  shade  lines  at  the  top,  but  in 
other  respects  the  method  of  drawing  is  the  same. 

In  the  shading  of  small  cylinders  the  effect  is  often  improved  by  shading  the  lower  side  only. 
Compare  Fig.  3  with  the  shaft  of  Fig.  5. 

Bell-shaped  surfaces  are  frequently  shaded  as  in  Fig.  2,  but  that  of  Fig.  .S  involves  no  cir- 
cular arcs  and  for  small  pieces  is  equally  good.  Fig.  8  represents  a  cone  shaded  by  parallel  lines 
in  a  manner  similar  to  the  cylinder.  The  usual  method  of  doing  this,  by  drawing  all  of  the  shade 
lines  radiating  from  the  vertex,  is  very  difficult,  requires  more  lines,  and  rarely  looks  as  well. 

The  pipe  shown  in  Fig.  7  illustrates  the  method  of  grading  the  lines  so  that  the  upper  and 
left-hand  portion  shall  represent  the  illuminated  parts.  Had  the  bend  been  to  the  right,  the  shad- 
ing would  have  been  more  simple.  The  conical  portion  of  the  pipe  flange  shows  yet  another 
method  that  may  often  be  used  to  advantage.  The  system  used  for  the  shading  of  the  sphere. 
Fig.  6,  will  be  apparent  from  the  illustration. 

It  is  rarely  necessary  to  shade  plane  surfaces  and  should  be  avoided  when  possible.  When  neces- 
sary to  emphasize  the  fact  that  a  plane  is  inclined  to  that  of  the  paper,  the  method  of  Fig.  9  may 
be  used. 

Fig.  27  illustrates  a  method  representing  knurled  surfaces.  The  angle  of  the  cross  lines  must 
be  varied  to  conform  to  the  ratio  of  diameter  to  length  of  surface,  for  it  will  be  observed  that  no 
change  is  made  in  the  spacing  until  a  series  of  lines  has  been  drawn  from  A  to  B.  The  spacing 
in  the  cut  is  slightly  exaggerated  to  better  illustrate  the  method. 


THE    TITLE. 


23 


The  Title. — The  title  of  a  drawing  should  always  be  placed  in  the  lower  right-hand  corner 
of  the  sheet,  and  should  designate,  first,  the  name  of  the  mechanism  ;  second,  the  name  of  the 
special  detail ;  third,  the  scale  ;  fourth,  the  date,  which  is  always  that  of  the  finishing  of  the  draw- 
ing. The  draftsman's  name  or  initials  should  be  printed  in  the  extreme 
corner.  Besides  this,  such  data  as  the  "  time  number,"  the  number  of  B 
drawings  belonging  to  this  special  machine,  and  other  data  may  be  given  ; 
but  the  information  essential  to  every  drawing  is  that  given  above. 

The  student  must  decide  for  himself  concerning  the  character  of 
type  to  be  used.  Several  styles  are  illustrated  in  the  plates.  That  most 
easily  acquired  is  shown  in  Plate  9,  but  it  is  not  so  clear  as  those  of 
Plates  3  and  7.  Plate  10  illustrates  a  most  excellent  style  but  rather 
difficult  to  execute  well.  The  round  writing  of  Plate  11  is  much  used, 
but  it  comprises  many  objectionable  forms  of  letters,  and  the  figures  are 
too  indistinct  to  be  used  on  the  dimension  lines.  Whatever  style  is 
adopted  should  be  adhered  to  until  it  can  be  rapidly  written,  and  always 
without  mechanical  aid. 

In  the  final  cleaning  of  the  sheet  it  should  be  borne  in  mind  that 
many  of  the  auxiliary  lines  used  as  construction  lines  may  be  useful  to 
the  pattern  maker,  or  possibly  to  the  draftsman,  at    some   later  day.     Thus 


Fic.  27 


It  IS  often   well   to 
leave  some  of  these  lines  on  the  drawing  even  though  it  may  present  a  less  neat  appearance. 


CHAPTER  III. 
Sectional  Views. 

Use  of  a  Section. — For  tlie  complete  representation  of  mechanism  it  is  frequently  nec- 
essary to  make  use  of  a  section  in  order  that  some  details  which  would  otherwise  be  hidden  may 
be  shown  in  full.  The  sectional  view  is  a  representation  of  the  object  after  it  has  been  cut  by  an 
imaginary  plane.  When  possible,  such  a  view  should  be  used  instead  of  introducing  numerous 
dotted  lines,  as  the  latter  tend  to  produce  confusion.  There  are  several  conventional  methods  of 
representing  the  surface  of  an  object  when  cut  by  a  plane.  That  most  commonly  used,  and  for 
most  purposes  the  best,  consists  of  parallel  lines  usually  drawn  at  an  angle  of  45°  across  the  cut 
surface.  By  changing  the  direction  of  these  lines  a  clear  distinction  may  be  produced  between 
the  parts  of  different  pieces  which  may  be  in  contact,  and  by  varying  the  character  of  the  lines,  a 
difference  in  material  may  be  indicated.      Plate  1 1  is  an  excellent  example  of  the  use  of  a  section. 

Section  Liners. — The  regulating  of  the  space  between  these  lines  is  frequently  done  by 
the  eye,  but  it  may  be  more  easily  and  rapidly  accomplished  by  the  use  of  a  section  liner.  This 
is  an  instrument  by  means  of  which  the  triangle  is  made  to  move  through  equal  spaces  fixed  by  a 
gauge  determined  by  the  draftsman,  and  thus  avoiding  the  care  and  time  usually  required  for  the 
performing  of  this  operation  by  the  eye.     Unfortunately,  however,  most  of  the  section  liners  to  be 


NOTATION   FOR   SECTION    LINING. 


25 


found  are  complicated  and  unsuitable  for  the  purpose.     No  more  simple  or  effective  tool  has  been 

designed  for  this  use   than  that  shown  by  Fig.  28,  which 

consists  of  a  strip  of  wood  not  over  an  eighth  of  an  inch 

thick,  having  parallel  edges  and  provided  with  a  stop  on 

either  end,  one  of  which  is  adjustable.     The    only  care 

necessary  to  be  observed  is  in  keeping  the  edges  of  the 

triangle  and  slide  together,  but  if  the  edge  of  the  latter 

is  placed  against  the  blade  of  a  T  square,  this  difficulty 

is  partially  overcome.     The  method  of  operating,  which 

scarcely    requires   explanation,    is    as    follows: — Having 

drawn  a  line  by  the  triangle,  in  the  position  shown,  by 

means  of  the  second  finger  push  the  triangle  against  stop 

B  while  holding  the  slide  firm  with  the  first  finger.   Next, 

while  holding  the  triangle  fast,  move  the   slide   until  stop  A   touches  the  triangle   and  draw  the 

second  line.     Of  course  practice  is  required  to  manipulate  the  two  pieces  with  ease  and  rapidity, 

but  the  saving  of  the  otherwise  necessary  strain  to  the  eyes  compensates  for  this. 

Notation  for  Section  Lining.— Plate  15  illustrates  the  various  types  of  sections  avail- 
able for  the  representation  of  ditferent  materials.  Save  in  the  case  of  cast-iron  (Fig.  1)  there  is 
no  general  agreement  among  draftsmen  as  to  the  material  which  each  type  of  lining  shall  desig- 
nate. Such  a  standard  was  proposed  to  the  American  Society  of  Mechanical  Engineers,*  but 
fortunately  failed  of  adoption.     It  would  only  have  added  one  more  complication  to  the  intrica- 


FlC.  28 


♦Transactions  of  the  A.  S.  of  M.  E.,  Vol.  IX,  page  107. 


26 


NOTATION   FOR    SECTION    LINING. 


cies  ot  modern  niacliine  drawing,  and  made  a  misunderstanding  possible.  If  the  slightest  doubt 
as  to  the  nature  of  the  material  represented  is  likely  to  occur,  write  the  name  of  the  material  on 
the  section.  No  type  of  sectioning  should  be  used  that  involves  the  making  of  two  widths  of  lines. 
Dotted  lines  should  be  used  sparingly  and  types  shown  by  figures  4  and  10  are  still  less 
desirable. 

In  the  illustrations  of  this  book  the  following  no- 
tation  has  been  used  for  section  lines.  Fig.  1  repre- 
sents cast-iron.  Fig.  2,  wrought-iron  and  steel. 
Fig.  3,  brass,  bronze,  etc.  Fig.  4,  Babbitt's  metal 
or  other  lining  metals.  Fig.  6,  brick.  Fig.  7,  wood, 
across  and  with  the    grain.     Fig.  8,  stone.  Fig.  9 

is  used  to  section  a  surface  which  is  invisible.     Fig.'s 
b  and  10  are  undesignated.       The  former  is  often  used 
to   produce   a  sharp   contrast  with  other  sections,  and 
fref|uently    employed    on   Patent  Office   work,  and  for 
illustrations  where  figures  and  figure  lines  are  omitted. 
Of  course   many  other  types  may  be  devised,  but 
it    rarely  occurs    that    the   variety    here    represented 
will  not  suffice.      Care  should   be  exercised  in   choos- 
ing the  spacing  for  section  lines  that  tiiey  be  not  too  fine.     No  rule  can  be  given  for  the  distance, 
which  woidd  he  almost  entirely  dependent  on  the  size  of  the  section  represented. 

Dotted  Sections. — In  some  c.Tses  it  is  necessary  to  represent  a  piece  of  mechanism   by  a 
full  or  external  view,  when  a  section  is  also  required  to  explain  some  little  details  of  it.       Instead 


Fic.  29 


COLORED    SECTIONS. 


27 


of  making  a  separate  sectional  view  it  may  often  suffice  to  dot  tlie  obscure  section,  either  by  the 
method  shown  in  Fig.  29,  one-half  of  which  shows  the  section  by  dotted  lines,  while  the  other 


^    V'.VVqVI'-'. 


Fig.  30 

half  represents  the  section  by  a  dotted  outline  only  ;  or  by  that  of  Fig.  30  in  which  the  dotted 
outline  is  emphasized  by  a  series  of  dashes.  This  second  method  may  be  employed  to  advantage 
when   penciling   a  somewhat  complicated  drawing   which    may  or   may  not  be  shown  in  section 


28  COLORED   SECTIONS. 

when  inked.  Thus  in  the  case  of  Plate  11,  illustrating  the  Tail  Stock  of  a  lathe,  the  lines  of  the 
penciled  drawing  would  be  much  confused  if  section  lines  are  omitted  until  the  inking  is  done. 
But  the  section  lines  should  never  be  drawn  in  pencil,  as  it  makes  the  inking  more  difficult, 
besides  necessitating  the  erasing  of  pencil  lines  among  inked  section  lines.  If,  however,  the 
section  be  indicated,  as  in  Fig.  30,  the  drawing  may  be  made  very  distinct,  and  the  penciled 
lines  or  dashes  be  drawn  so  fine  as  to  require  no  erasing. 

Colored  Sections.— It  is  unfortunate  that  reproductive  processes,  such  as  blue-printing, 
make  the  use  of  color  for  sectioning  impracticable.  It  is  in  every  respect  the  best  method  of  repre- 
senting them,  for  by  varying  the  shade,  adjoining  pieces  of  like  material  may  be  clearly  shown, 
and  by  changing  the  color,  the  character  of  the  metal  may  be  expressed.  The  time  required  to 
perform  the  work  is  also  much  lessened.  Where  the  system  of  tracing  a  drawing  is  still  employed, 
this  method  may  be  used  instead  of  section  lining,  as  is  already  done  in  many  locomotive  works 
where  the  tracing,  instead  of  the  drawing,  is  placed  on  file.  The  practice  of  sending  to  the  shop 
a  drawing,  instead  of  a  tracing  or  blue  print,  is  one  to  be  commended,  as  the  best  copy  is  then 
placed  in  the  hands  of  the  man  who  finds  the  most  difficulty  in  reading  a  drawing. 

When  colored  inks  are  used  for  section  lining,  the  metal  may  be  designated  by  the  color  of 
the  line  instead  of  by  the  character  of  the  section  line.  Black  is  always  used  for  cast-iron  ;  Prus- 
sian blue  for  wrought-iron  and  steel;  yellow  ochre,  or  Indian  yellow,  for  brass,  (a  very  little 
carmine  added  to  the  yellows  will  give  more  body  to  them),  burnt  sienna  and  burnt  umber  for 
wood,  and  sometimes  for  leather. 

Choice  of  Cutting  Planes.— In  representing  an  object  in  section,  choose  such  a  position 
for  the  cutting  plane  that  all  of  the  details  requiring  to  be  shown  shall  be  seen  in  the  clearest 
manner. 


CUTTING    PLANES. 


29 


t*ortions  of  the  object  lying  berjond  the  cutting  plane 
need  not  be  shoivn  on  the  sectional  view  unless  it  may  be 
tliought  desirable.  In  Fig.  33  the  flange  bolts  lying  beyond 
the  plane  are  not  shown,  since  it  would  only  add  to  the  labor 
of  drawing  and  produce  confusion  as  well. 

l^ke  pla7ie  of  the  section  need  not  be  continuous.  The 
sectional  view  of  the  Tail  Stock,  Plate  11,  includes  a  section 
made  by  two  planes,  but  no  confusion  need  arise  from  this, 
and  in  actual  practice  the  note  concerning  the  plane  on  which 
the  section  is  made  might  be  omitted. 

All  that  lies  within  the  cutting  plane  need  not  be  sec- 
tioned. 

Fig.  31  illustrates  a  cylindrical  piece  with  hub,  ears,  and 
ribs.  Two  sectional  views  are  shown,  the  lower  figure  repre- 
senting the  object  as  cut  by  the  plane  A  B,  the  section  passing  | 
through  one  rib,  the  central  hub,  and  one  ear.  The  other 
section  is  the  conventional  representation  of  the  surface  cut  by 
the  same  plane.  In  this  case  the  ear,  rib,  and  central  hub  are 
omitted  from  the  section,  but  shown  as  though  they  were  imme- 
diately behind  it.  A  good  illustration  of  this  case  is  also  seen 
in  Fig.  32  which  illustrates  the  conventional  method  of  drawing 
gears,  hand  wheels,  pulleys,  etc.  Here  the  plane  A  B  passes 
through  a  tooth  and  arm,  but  the  sectional  view  shows  both  in 


FIG.  31 


/VrYfV^ 


'mm^ 


^?^w^ 


Fic.32 


CUTTING    PLANES. 


31 


full.  The  key  and  shaft  are  also  drawn  in  full,  although 
lying  in  the  cutting  plane.  In  general  do  not  section 
such  details  as  a  shaft,  a  key,  a  bolt,  a  gear  tooth,  or 
the  arm  of  a  wheel. 

A.  section  of  a  syinmelrical  jjiece  .s/ioulJ  be  sug- 
gestive of  symmetry.  In  the  correct  sectional  view 
of  Fig.  32,  both  ears  and  ribs  are  shown  as  though 
they  were  two,  four,  or  six,  instead  of  three,  but  a 
note  signifying  the  number  of  each  is  a  sufficient  expla- 
nation. Again,  in  the  case  of  the  stuffing-box  gland, 
Fig.  33,  the  ears  are  better  shown  in  full,  if  they  are 
small  in  comparison  with  the  diameter  of  the  gland. 
The  discretion  of  the  draftsman  must  be  used  in  show- 
ing of  the  flange  bolts  since  they  may  be  drawn  in  full, 
or  dotted  as  in  the  figure  ;  but  in  either  case  their  true 
relation  to  the  cylinder  should  be  shown.  To  project 
the  bolt,  shown  at  the  left-hand,  from  its  position  as 
drawn  in  the  top  view,  would  add  nothing  to  the  infor- 
mation required,  but  rather  tend  to  mislead. 

In  the  illustration  of  the  Rear  Bearing  for  the 
Screw  Polishing  machine,  Plate  8,  an  exception  was 
made  to  this  principle  by  reason  of  the  confusion  which 
would  otherwise   have  been  produced    by  the   section 


Fig.  33 


32 


BROICEN   SECTIONS. 


lines  being  drawn  across  the  slotted  space  for  leather.     In  actual  practice,  the  piece  would  be  sec- 
tioned so  as  to  appear  symmetrical. 

Broken  Sections. — When  a  portion  of  a  rod,  bar,  pipe,  or  other  symmetrical  piece  is  shown 
as  broken,  the  section  should  be  suggestive  of  the  shape.  Fig.  34  represents  a  cylindrical  rod. 
Fig.  35,  a  bar  of  rectangular  section.  Fig.  36,  a  pipe.  Fig.  37,  a  rod  of  wood.  The  outlines 
of  these  sections  may  be  drawn  with  an  ordinary  pen,  but  the  lines  should  not  be  jagged  save  in 
the  representation  of  wood,  as  in  Fig.  37. 


Fic.  36 


Fic 


It  is  quite  common  to  show  the  section  made  by  a  plane  at  right  angles  to  a  view,  upon  the 
view  itself.  The  sections  of  the  gear  arm.  Fig.  32,  made  by  the  planes  E  F  and  G  H  illus- 
trate this. 

Figuring. 

After  the  inking  of  a  drawing  is  completed,  and  before  the  section  lines  are  drawn,  the  figure 
lines  are  required  to  be  put  on.  This  is  the  most  important  part  of  the  making  of  a  drawing,  and 
requires  the  greatest  care  and  most  experience.  Unfortunately,  at  this  stage  the  student,  and  not 
unfrequently  the  draftsman,  becomes  wearied  with  his  work,  and  the  subsequent  operations  are  too 
often  hurriedly  and  carelessly  performed.      While  it  may  frequently  be  necessary  to  make  haste  in 


tiGUBlNG.  33 

the  figuring  of  a  drawing,  it  must  never  be  hurriedly  done  and  the  most  scrupulous  care  should  be 
exercised  in  the  drawing  of  every  dimension  line,  and  the  making  and  checking  of  every  figure. 

As  an  illustration  of  the  method  to  be  employed  in  the  figuring  of  a  drawing,  consider  the 
case  of  the  stub-end,  Plate  5.  Suppose  the  drawing  be  in  readiness  to  figure.  We  have  first  to 
consider  the  class  of  mechanics  for  whom  this  drawing  may  be  made.  In  general,  the  needs  of  the 
pattern-maker  are  first  to  be  thought  of;  but  inasmuch  as  a  pattern  serves  for  many  duplicate 
pieces,  the  dimensions  of  unfinished  parts  may  usually  be  omitted.  In  such  cases  the  draftsman 
will  furnish  the  pattern-maker  with  a  sketch  or  tracing  having  the  necessary  figures.  This  will 
save  the  crowding  of  the  drawing  with  figures  which  when  once  used  are  not  likely  to  be  required 
attain.  If  the  drawing  is  to  be  sent  to  a  distance  where  detailed  information  may  not  be  readily 
obtained  from  the  draftsman,  these  figures  must  not  be  omitted  from  tiie  drawing. 

The  requirements  of  the  forge  shop  are  usually  met  by  sketches  specially  prepared  for  that 
department,  but  the  figures  given  for  the  machinist  will  ordinarily  suffice  for  the  smith.  In  giving 
dimensions  for  either  pattern-maker  or  smith,  specify  finished  sizes  only,  leaving  the  amount  of  shrink 
or  finish  required,  to  his  judgment.  In  the  case  cited,  figures  for  the  machinist  only  have  been  given. 

It  is  customary  to  draw  the  figure  lines  in  blue  ink  and  the  center  lines  in  carmine,  but  this 
order  may  be  reversed,  or  one  color  used  for  both.  If  colors  are  used  for  these  lines  they  are  bet- 
ter drawn  full.  Begin  by  drawing  the  dimension  lines  necessary  for  locating  the  center  lines  and 
working  faces.  In  the  connecting  rod  the  diameter  and  length  of  the  pin,  or  box  for  same,  is  the 
first  consideration.  Next  locate  end  of  rod  C,  after  which  completely  figure  that  part  by  dimen- 
sion lines  marked  D,  E,  F,  G,  H,  I,  J,  K,  L.  Then  consider  the  gib  and  key  O,  P,  R,  S,  etc. 
Next,  the  set-screw  and  strap,  and  finally,  figure  the  boxes,  if  figures  given  for  other  parts  do  not 
already  include  these. 


Si  FIGURING. 

The  dimension  lines  being  completed,  the  center  lines  should  next  be  drawn,  after  which  the 
witness  marks  (or  arrow  points)  and  figures,  are  to  be  made.  The  drawing  should  then  be  cleaned 
and  finally  section  lined. 

In  figuring  detailed  drawings  like  Plates  7  and  8,  great  care  is  necessary  to  avoid  mistakes,  and 
the  draftsman  will  always  do  well  to  examine  carefully  the  figures  on  all  parts  that  fit  together. 
Thus  the  diameter  and  length  of  the  bearings  must  accord  with  the  dimensions  for  the  spindle  fitting 
the  same. 

The  dimensions  on  a  drawing  should  always  indicate  the  full  size,  and  are  independent  of  the 
scale  to  which  the  drawing  may  be  made.  In  connection  with  this  it  is  well  to  note  that  the  scale 
dimensions  of  a  drawing  should  never  be  spoken  of,  as  great  confusion  would  arise  from  it.  To 
illustrate  :  let  us  suppose  a  shaft  eight  inches  in  diameter  to  be  drawn  one-quarter  size.  It  would 
then  measure  two  inches,  but  should  never  be  spoken  or  thought  of  as  other  than  eight  inches,  the 
real  diameter ;  and  if  the  draftsman  was  asked  to  add  an  inch  to  the  diameter  it  is  his  business  to 
see  that  the  proper  increase  is  made  according  to  the  scale  which  he  may  be  using.  In  this  case 
he  would  have  to  add  one  quarter  of  an  inch  to  the  diameter  as  drawn,  but  it  must  always  be 
spoken  of  as  one  inch. 

Rules  to  be  Observed  in  Figuring  Drawings. 

1.  Dimension  and  witness  lines  should  be  made  in  blue  ink,  centre  lines  in  carmine,  arrow 
points  and  figures  in  black. 

2.  Dimension  lines  may  be  continuous  or  broken,  as  •* >■    ■< *■ 

The  latter  form  is  of  advantage  only  in  indicating  the  position  to  be  occupied  by  the  figure. 


S-IGURING. 


35 


3.  Centre  lines  should  never  be  used  as  dimension  lines. 

4.  Dimension  lines  should  not  be  too  close  to  line  of  the  object. 

5.  Make  arrow  point  or  witness  point  thus  ■< and  never   < 

6.  Make  the  arrow  points  exactly  touch  the  lines  to  which  the  dimensions  are  given. 

7.  Give  dimensions  overall,  as  well  as  sub-dimensions. 

8.  Exercise  great  care  in  the  making  of  figures,  adopting  some  plain  type,  and  as  far  as 
possible,  using  one  size. 

9.  Separate  the  numerator  and  denominator  of  a  fraction  by  a  horizontal  line  thus,  (|)  never 
using  an  inclined  line  for  this  purpose.  (The  horizontal  line  may  be  omitted,  by  writing  the 
figures  above  and  below  the  dimension  line,  as  < — • 1 >). 

10.  Write  the  figures  in  line  with  the  dimension  line,  and  never  inclined  or  perpendicular 
to  it. 

11.  Figures  should  face  bottom  and  right  side  of  drawing. 

12.  If  all  dimensions  are  in  inches,  the  inch  mark  '  need  not  be  used,  but  when  feet  and 
inches  are  to  be  represented,  write  as  follows,  3  Ft.  6",  or  if  the  foot  mark  '  is  used  the  figures 
should  be  separated  thus,  3'— ^6'. 

13.  AVhen  using  large  and  small  dimensions  on  the  same  drawing  it  is  well  to  express  all 
dimensions  less  than  three  feet  in  inches,  and  larger  ones  in  feet  and  inches,  thus  29'    3'^— 0 

3 5". 

14.  First  figure  that  view  which  illustrates  most  completely  the  details  of  the  object. 

15.  In  general,  do  not  repeat  figures. 

16.  Figure  to  centre  lines  and  faced  surfaces. 

17.  Figure  diameter  of  circle,  in  preference  to  radius,  and  draw  the  line  at  an  angle. 


36  FINDING   DIMENSIONS. 

18.  If  the  radius  be  used  instead  of  diameter,  locate  clearly,  as,     -<^—^" ^•*-^' 

19.  Do  not  draw  section  lines  across  the  figures. 

20.  In  correcting  a  figure  without  altering  the  drawing,  affix  the  word  "  make,"  which  in- 
dicates a  knowledge  on  the  part  of  the  draftsman  of  the  existing  discrepancy  in  the  drawing. 

Finding'  Dimensions. — The  figure  for  a  special  part  may  be  more  readily  found  by  first 
looking  for  the  arrow  point  toucliing  one  of  the  lines  limiting  this  part.  If  the  point  is  not  to  be 
found  on  one  view,  seek  for  it  on  other  views,  and,  failing  to  find  it,  the  figure  may  be  declared 
missing.  To  illustrate,  sui^pose  the  combined  widtli  of  gib  and  key  of  the  connecting  rod,  Plate 
5,  is  required.  Beginning  at  the  top  of  the  key  we  find  tiie  first  arrow  [Joint  leads  to  the  dimen- 
sion W,  the  second  to  the  dimension  E,  the  third  to  the  required  dimension  O.  This  method 
will  greatly  facilitate  the  finding  of  figures  on  complicated  drawings,  and  enable  the  workman  to 
determine  quickly  whether  the  figure  be  missing. 

Method  of  indicating'  surfaces  vvliicli  are  to  be  ftni,slied. — Although 
this  does  not  properly  come  under  the  head  of  the  suliject  of  figuring,  yet  it  often  has  to  be  con- 
sidered at  the  same  time.  On  many  drawings  in  all  shops  it  is  unnecessary  to  give  this  informa- 
tion, and  in  many  shops  it  is  never  given.  But  where  drawings  are  elaborately  detailed  and  the 
work  of  construction  much  subdivided,  it  is  often  necessary  to  iildicate  this  on  the  drawing.  It 
may  be  done  by  writing  the  word  "  finish,"  or  simply  the  letter  "  f  "  across  the  line  representing 
the  surface  to  be  finished.  Or  a  colored  ink  may  be  used  to  draw  a  line  parallel  with  the  surface 
to  be  finished.  This  latter  method  is  objectionably  from  the  confusion  caused  by  the  increased 
number  of  lines,  but  may  be  used  to  advantage  on  blue  prints  by  using  carmine  and  soda  water 
for  the  ink.     This  distinguishes  the  finish  line  from  all  others. 


technical  sketching.  37 

Technical  Sketching. 

The  ability  to  make  a  free-hand  technical  sketch  of  a  piece  of  mechanism  is  of  more  impor- 
tance to  most  mechanics  than  that  of  making  the  ordinary  mechanical  drawing  with  instruments. 
Unfortunately,  however,  it  requires  much  more  skill  to  do  this,  not  because  of  the  practice  required 
for  the  clever  handling  of  the  pencil,  but  by  reason  of  the  difficulty  in  executing  a  drawing  without 
the  mechanical  checks  to  errors  of  judgment  in  the  representation  ;  and  also  because  of  the  neces- 
sity of  a  more  concise  expression  of  the  idea  than  would  be  given  in  the  drawing.  Moreover,  a 
thorough  knowledge  of  projection  and  the  principles  of  machine  drawing  are  as  requisite  to 
technical  sketching  as  to  technical  drawing.  The  enumeration  of  these  difficulties  is  not  for  the 
purpose  of  discouraging  the  student,  but  rather  to  direct  his  energies  toward  gaining  a  mastery  of 
the  most  efficient  method  of  technical  expression. 

One  of  the  most  important  functions  of  the  sketch  is  in  the  development  of  a  design.  At 
such  a  time  the  engineer  cannot  resort  to  the  more  laborious  process  of  instrumental  drawing,  but 
must  rapidly  express  his  thoughts  by  free-hand  sketches.  Some  of  these  preliminary  sketches 
may  be  as  complete  in  the  important  details  as  the  more  elaborate  drawing  which  the  draftsman 
must  finally  make  for  the  shop  use. 

Practice  in  acquiring  this  invaluable  art  of  rapidly  and  clearly  expressing  one's  technical  ideas 
may  be  acquired  in  several  ways.  Tiiat  most  to  be  commended  is  the  practice  of  sketching 
directly  from  the  object  according  to  the  method  hereinafter  explained.  A  perspective  or  isometric 
representation  is  often  useful  as  a  substitute 'for  many  views,  or  to  more  sharply  define  certain 
obscure  details,  but  if  the  student  is  unfamiliar  with  these  methods,  the  orthographic  representation 
will  suffice  for  all  cases.. 


38  TECHNICAL    SKETCHING. 

When  it  is  not  possible  to  obtain  models  from  which  to  work,  a  good  exercise  will  be  found 
in  a  free-hand  detailing  of  the  parts  of  a  finished  drawing,  after  which  the  sketch  may  be  tested  by 
making  the  assembled  drawing  from  it. 

A  most  valuable  training,  both  in  sketching  and  in  observation,  may  also  be  had  from 
memory  sketches.  For  this  purpose  choose  some  simple  model  or  the  drawing  of  a  plain  object, 
and,  having  carefully  studied  it,  set  it  aside  and  make  a  free-hand  drawing  comprising  two  or 
three  views. 

In  the  making  of  all  sketches,  establish  first  the  center  lines  and  important  details  as  would 
be  done  in  the  making  of  a  drawing,  and  in  general,  proceed  in  a  similar  manner. 

Order  to  be  observed  iu  the  making-  of  a  .sketch  from  mechanism  already 
constructed. — First :  Having  separated  the  different  parts  of  the  machine,  sketch  each  in  detail, 
omitting  nothing  necessary  to  its  complete  representation.  Use  written  notes  whenever  they  may 
save  the  time  of  drawing.  Complete  the  sketches  of  every  part  before  putting  on  any  dimension 
lines. 

Second  :  Sketch  all  the  necessary  dimension  lines  with  the  arrow  points,  but  do  not  figure 
the  sketch.  Tiiere  are  reasons  for  doing  this.  It  insures  a  more  thorough  figuring  of  the  draw- 
ing, as  one  is  not  diverted  from  the  consideration  of  the  dimensions  wanted,  by  the  measuring  of 
the  pieces  and  writing  of  the  figures  ;  it  is  productive  of  neater  work,  since  one  is  not  required  to 
handle  the  pieces  which  are  likely  to  be  coated  with  oil  or  covered  by  dust ;  it  enables  the  work  to 
be  more  rapidly  and  easily  done,  since  it  may  be  executed  at  the  desk,  without  reference  to  the 
pieces  save  through  the  sketch.  This  will  also  involve  a  critical  reading  of  the  sketch,  and  serves 
as  a  check  to  errors  of  drawing. 

Third ;  Obtain  the  figures  for  the  dimension  lines  indicated  on  the  sketch. 


PRACTICAL    SUGGESTIONS.  39 

Practical  Suggestions.— The  sketch  and  its  dimensions  should  accurately  represent  the 
object  illustrated.  It  does  not  follow,  however,  that  the  drawing  subsequently  made  from  this 
sketch  shall  be  a  duplicate  representation  of  the  pieces  sketched.  Drawings  made  from  existing 
mechanisms  are  intended  to  reproduce  that  which  the  machine  was  designed  to  be,  rather  than  to 
copy  the  piece  already  constructed.  If  an  attempt  be  made  to  suggest  these  alterations  on  the 
sketch,  confusion  is  very  likely  to  arise.  It  frequently  happens  that  the  dimension  of  a  piece  may 
be  found  to  involve  sixteenths  or  thirty-seconds  of  an  inch  when  integers  or  halves  or  quarters 
would  serve  as  well :  thus,  if  the  diameter  of  a  flange  was  found  to  measure  12^L  inches,  it  would 
ordinarily  be  inferred  that  12  inches  was  meant,  although  the  former  dimension  should  appear  on 
the  sketch. 

Use  one  view  if  possible,  and  do  not  overcrowd  the  sketch  with  details. 

Exercise  such  care  in  the  making  of  the  sketch  as  shall  enable  it  to  be  readily  used  by  any 
one  familiar  with  the  technique  of  drawing.  The  character  of  a  sketch  too  frequently  implies  the 
supposition  that  it  is  intended  solely  for  the  draftsman  who  made  it,  and  not  unfrequently  many 
details  are  omitted  to  be  supplied  by  the  memory.  For  the  information  which  it  is  intended  to 
convey,  the  sketch  should  be  as  complete  as  a  drawing. 

When  practicable,  it  is  well  to  sketch  those  parts  which  may  be  mechanically  related  so  that 
reference  may  be  readily  made  from  one  to  the  other. 

Sketch  objects  in  their  proper  position,  for  it  is  better  thus  to  suggest  the  true  relation  of  the 
lines  and  surfaces,  although  the  dimensions  alone  are  to  be  relied  on  to  determine  them. 

The  center  lines  should  always  be  drawn  with  care,  and  the  position  of  dimension  lines 
determined  as  in  the  case  of  a  drawing,  save  that  in  the  latter  case  more  will  be  required.  Figure 
each  piece  independent  of  others.  Thus,  in  the  case  of  a  shaft  and  its  bearings,  the  diameter  will 
appear  on  each. 


40  1'ractical  suggestions. 

Every  draftsman  sliould  acquire  tlie  habit  of  preserving  his  sketches,  especially  those  made  in 
connection  with  the  design  of  a  machine,  for  it  not  unfrequently  happens  that  an  apparently  value- 
less sketch  which  has  been  destroyed  becomes  necessary  to  the  complete  development  of  a  detail, 
or  invaluable  as  a  matter  of  record.  Two  kinds  of  sketch  books  have  become  a  part  of  the  para- 
phernalia of  the  modern  drafting  room  ;  one  in  which  is  made  or  filed  sketclies  suggestive  of  various 
designs  and  alterations  in  machinery  ;  the  other,  a  copy  book  in  which  may  be  preserved  a  copy 
of  every  sketch  sent  from  the  drafting  room. 


CHAPTER  IV. 
Examples  for  Practice. 

Problem  1,  Plate  1.— Assembled  drawing  of  a  Locomotive  Parallel  Rod.  The  planning 
of  this  sheet  is  so  simple  as  to  require  no  sketch  ;  but  since  the  principles  involved  do  not  differ 
from  those  of  the  "  lay-out  "of  the  most  complicated  drawing,  it  is  expedient  that  the  student 
should  perform  this  work.  The  size  of  the  sheet  witliin  the  margin  line  shall  be  10x14  inches. 
Two  views  are  required  and  are  best  arranged  as  shown  in  the  "  lay  out  "  sketch.  The  scale  of 
the  drawing  will  be  determined  by  the  dimensions  marked  D,  E  and  F,  the  sum  of  which  when 
drawn  cannot  be  greater  than  10  inclies,  and  should  be  considerably  less  to  allow  for  the  title, 
which  will  require  from  1  J  to  2  inches.  The  sum  of  tlie  dimensions  D,  E  and  F  according  to  the 
sketch  is  12  inches,  which  prevents  the  use  of  a  full  size  scale  but  makes  the  half-size  possible,  as 
it  would  require  but  6  inches,  leaving  4  inches  for  title,  space  between  the  views,  and  space  at 
top.  Having  determined  H,  K  and  L,  so  as  to  enable  the  drawing  to  present  the  most  symme- 
trical appearance,  the  center  lines  may  be  drawn.  It  should  previously  have  been  observed  that 
the  length  of  the  parallel  rod  is  such  as  to  preclude  the  possibility  of  drawing  it  even  at  half  or 
quarter  scale  without  illustrating  the  bar  as  broken,  which  may  of  course  be  done,  leaving  suf- 
ficient space  on  either  end.  The  only  section  requiring  to  be  shown  is  that  of  the  rod,  which  may 
be  drawn  as  suggested  by  the  sketch.  The  practice  to  be  derived  from  the  use  of  shade  lines  on 
this  drawing  should  not  be  neglected.     For  the  purposes  of  study  it  is  well  to  draw  the  dimen- 


42  EXAMPLES    FOU    PRACTICE. 

sion  lines  in  pencil,  so  that  they  may  be  well  considered  and  changed  if  necessary,  but  in  prac- 
tice they  should  be  drawn  in  ink  at  first.  Figure  the  drawing  so  that  the  dimension  of  every  de- 
tail may  be  obtained. 

Problem  3,  Plate  3. — Assembled  drawing  of  a  Boiler  Check  Valve.  This  is  to  be  shown 
complete  with  the  valve  on  its  seat,  the  cap  screwed  down,  and  the  coupling  nut  partly  on.  One 
view  is  quite  sufficient  for  illustrating  every  detail,  but  it  is  desirable  to  draw  a  side  view  to  obtain 
the  practice.  The  principal  view  should  be  sectioned  and  the  character  of  the  metal  designated 
by  the  character,  or  color,  of  the  section  line. 

Problem  3,  Plate  3. — Detailed  Drawing  for  a  2  inch  Globe  Valve.  All  of  the  parts  are 
to  be  shown  separately,  in  like  manner  to  those  of  Plates  7  and  8,  but  on  one  sheet.  The  lay-out 
of  this  sheet  will  require  a  careful  study,  involving  the  consideration  of  the  number  and  character 
of  the  views.  Because  two  views  of  any  of  the  parts  are  shown  on  the  plate,  it  does  not  follow 
that  the  details  should  be  similarly  treated. 

A  more  difficult  but  most  excellent  treatment  of  this  problem  would  be  the  making  of  a  free- 
hand detailed  sketch  of  the  valve,  figuring  the  same  completely.  Then,  putting  aside  the  plate, 
make  the  assembled  drawing  from  these  sketches.  Either  of  these  methods  will  require  much 
more  time  than  may  at  first  appear  necessary,  but  to  faithfully  and  accurately  produce  one  such 
drawing  is  worth  a  dozen  thoughtlessly  executed. 

Problem  4,  Plates  4,  5  ami  6. — The  drawing  of  a  connecting-rod  involves  an  excellent 
problem  in  the  intersection  of  surfaces,  and  this  should  be  thoroughly  mastered  before  proceeding 
with  the  drawing  of  the  rod.  As  the  principles  involved  are  applicable  to  many  practical  prob- 
lems it  is  desirable  that  the  student  should  make  a  careful  study  of  each  of  the  cases  shown. 

Fig".  2,  Plate  -4,  represents  a  cylinder   terminating  in  a  bell-shaped  end,  and    because  the 


EXAMPLES    FOR    PRACTICE.  43 

surface  may  be  generated  by  the  motion  of  a  line  about  an  axis,  it  is  known  as  a  surface  of  revo- 
lution. The  end  view  of  this  surface  is  shown  as  cut  by  four  planes,  A  B,  C  D,  A  C,  B  D,  parallel  to 
the  axis,  and  tlie  appearance  of  the  object  after  having  been  cut  is  shown  by  Fig".  1,  The  prob- 
lem consists  of  finding  the  curve  of  intersection  E  F  G,  together  with  a  similar  curve  on  the  upper 
surface  which  would  be  shown  on  another  view. 

Fig".  3  illustrates  the  same  case  without  the  line  shading.  Three  views  of  the  cylinder  with 
its  bell-shaped  end  are  shown,  but  they  ai-e  represented  as  cut  by  the  planes  A^  B"  and  B^  D**, 
producing  the  intersecting  curves  B''  G''  D''  and  A^  H'^  B'  wiiich  it  is  required  to  find.  Since  the 
points  A^,  B*  and  D^  lie  on  the  surface  of  the  cylinder  and  at  its  intersection  with  the  bell-shaped 
end,  their  projection  on  the  other  views  must  be  at  the  points  marked  by  the  corresponding  letters 
in  these  views.  The  limiting  points  H  and  G  of  the  curve  of  intersection  are  readily  determined 
by  extending  the  lines  B"'  C  and  B^  C^  until  they  cut  the  curve  at  the  points  H'  and  G^.  The 
top  view  of  the  point  H''  must  lie  between  A^  and  B^  and  directly  over  H''.  Similarly  project  G^  on 
to  the  front  view  at  G''.  It  remuins  only  to  determine  the  intermediate  points  in  the  curves. 
Pass  any  plane,  K  L,  perpendicular  to  the  axis ;  this  will  intersect  the  curved  surface  in  a  circle 
shown  on  the  side  view  by  O^  P^  M'  N* ;  but  this  circle  would  be  intersected  by  the  plane  A*  B' 
and  B^  D^  at  the  points  O^  P'  M^  and  N^,  and  hence  these  points  will  be  points  common  to  the 
two  surfaces,  and  therefore  points  of  the  curve  of  intersection.  Projecting  these  points  on  to 
the  front  and  top  views  will  have  determined  two  points  in  each  curve.  In  like  manner  obtain 
other  points. 

The  following  practical  application  differs  from  the  preceding  only  in  that  the  curve  of  the  bell- 
shaped  piece  is  not  located.  Fig.  4  illustrates  this  case  and  is  the  same  stub-end  as  that  shown 
in  Plate  5.      In  the  sketch  we  shall  have  those  dimensions  given  which  are  indicated  by  the  figure 


44  EXAMPLES    FOR    PRACTICE. 

lines  of  Fig.  4,  but  it  will  be  seen  that  neither  of  the  points  H"  or  G^  are  given  and  the  position  of 
the  center  X  is  unknown.  As  the  curve  of  the  bell-shaped  piece  is  tangent  to  the  neck  of  the  rod, 
the  diameter  of  which  is  given,  it  is  only  necessary  to  obtain  one  point  in  this  curve  to  fix  its  posi- 
tion. This  is  to  be  determined  by  revolving  the  point  B''  until  it  lies  in  the  plane  of  the  paper. 
To  do  this  an  end  view  will  be  required,  but  since  economy  in  the  use  of  lines  is  advisable,  let 
the  line  B''  V  represent  the  center  line  of  this  end  view,  and  the  rectangle  B''  W  Y  V,  the  half 
end  view  of  the  stub-end.  As  W  is  the  end  view  of  the  point  B''  we  may  obtain  its  extreme  dis- 
tance from  the  axis  which  may  be  laid  off  on  the  front  view  at  R,  thus  determining  the  revolved 
position  of  B''  and  the  required  point  in  the  curve.  Through  this  point  and  tangent  to  the  neck 
of  the  rod,  with  the  given  radius,  describe  the  arcs  representing  the  bell-shaped  portion,  observing 
that  all  of  the  centers  must  be  in  the  same  line  X  X.  These  arcs  will  determine  the  limiting  points 
of  the  curves  of  intersection,  and  intermediate  points  may  be  found  as  in  the  preceding  problem 
and  as  illustrated  in  this  figure. 

The  method  of  penciling  one  view  directly  over  anotiier  is  commonly  used  when  the  view  is 
to  serve  no  other  purpose  than  that  of  determining  lines  of  intersection. 

Fig'.  5  illustrates  a  case  in  which  the  cutting  plane  is  tangent  to  the  diameter  of  the  cylinder. 
Determine  the  curve  from  the  dimensions  given,  using  the  side  view  only  for  the  purpose  of  ob- 
taining the  curve  of  intersection  and  in  the  manner  illustrated  in  tiie  preceding  problem. 

The  action  of  a  gib  ami  liey  to  produce  motion  of  the  strap  for  taking  up  the  wear  in 
the  boxes  is  illustrated  by  Fig.  .38.  A  represents  the  stub-end,  B  and  C  the  boxes,  D  the  strap, 
E  the  key,  and  F  the  gib.  The  parts  are  shown  in  such  relative  position  as  would  exist  in  a 
newly  fitted  connecting  rod.  The  box,  B,  bears  against  the  end  of  the  rod,  A,  and  is  immovable, 
all  of  the  motion  due  to  the  wear  of  the  boxes  being  made  by  C.     In  order  to   move   the    box  C, 


EXAMPLES    FOK    PRACTICE. 


45 


toward  B,  the  strap  D  must  be  made  to  move  to  the  right.  This  is  accomplished  by  driving 
down  the  taper  iiey,  E,  so  as  to  increase  the  distance  between  the  parallel  faces  of  gib  and  key, 
and  since  there  can  be  no  motion  to  the  left,  the  gib  is  moved  to  the  right,  and  with  it  the  strap 
against  which  it  bears. 


Fic.  38 

The  Assembled  Drawing  ot  a  Coimectiug  Rod,  the  sketches  for  which  are  given 
on  Plate  6.     This  drawing  will  be   made  similar  to  that  of  Plate  5.     As   this  is  designed  to   be 


46 


EXAMPLES    FOR    PRACTICE. 


drawn  on  a  10x14  inch  slieet,  it  is  evident  that  a  full  representation  is  impossible,  but  the  lay-out 
sketch  will  enable  the  scale  to  be  determined.  In  obtaining  the  curve  of  intersection  on  the  rod» 
do  not  draw  a  special  end  view  but  use  the  method  of  Fig.  4,  Plate  4. 

Problem  5,  Plate  9. — Detail  of  casting  of  the  base  for  a  Back  Rest.     Two  views  of  a 


Fic.  39 

back  rest  for  a  milling  machine  are  given,  to  draw  the  details  of  the  base,  illustrating  it  by  three 
views.  The  representation  given  in  the  plate  was  chosen  to  show  the  use  of  a  dotted  section  and 
the  advantages  to  be  derived  from  the  omission  of  shade  lines  on  cylindrical  surfaces.  Without 
the  use  of  these  systems  it  would  be  very  difficult  to  show  ail  of  the  details  by  two  views.  The 
only  detail  omitted  is  that  of  the  clearance  curve  cut  from  the  base  for  the  adjusting  nut.  In  the 
front  view  this  nut  is  shown  in  full  section,  save  where  it  is  concealed  by  the  casting.  The 
dotted  section  of  the  side  view  is  that  made  by  a  plane  through  the  center  of  the  slide. 


EXAMPLES    FOR    PRACTICE.  4T 

Of  course  it  would  be  desirable  to  detail  all  of  the  parts  of  the  back  rest  as  well  as 
the  one  specified. 

Problem  G,  Plates  7  and  8,  (see  also  Fig.  39).  The  Assembled  Drawing  of  a  Screw 
Polishing  Machine.  One  view  only  is  required  for  the  drawing  of  this  machine,  and  it  may  be 
drawn  on  a  10x14  inch  sheet.  Nearly  all  of  tlie  parts  will  have  to  be  shown  in  section  and  some 
of  the  minor  details  of  the  parts  will  have  to  be  explained  by  notes,  such  as  the  slots  in  the  Bearing 
Nuts,  Plate  7.  The  details  for  a  leather  washer  and  the  oil  feeder  are  shown  in  Fig.  39.  Observe 
that  the  spring  here  shown  is  that  detailed  on  Plate  8,  but  must  be  shown  as  compressed  when 
drawn  in  its  proper  relation  to  the  other  parts.  After  having  determined  tiie  lay-out,  begin  the 
drawing  by  locating  the  center  line,  and  position  of  bearings  with  relation  to  the  casting,  as  given 
in  Fig.  39.  Then,  without  completing  any  of  the  details,  determine  the  position  of  pulleys,  collar, 
tail  screw,  etc.  Be  sure  that  proper  provision  has  been  made  for  taking  up  the  wear  of  the  boxes. 
In  order  to  avoid  confusion  it  may  be  found  desirable  to  indicate  the  different  pieces  by  sectioning 
them  in  pencil  as  directed  on  page  27. 

A  good  method  of  illustrating  the  degree  of  a  taper  is  shown  on  the  detail  of  the  bearings, 
Plate  8.  This  signifies  an  increase  in  the  radius  of  one-tenth  of  an  inch  for  every  inch  of  length. 
If  the  taper  is  designated  by  figures  without  the  lines,  it  is  always  questionable  whether  the  in- 
crease is  in  the  diameter  or  the  radius.  In  practice,  the  taper  would  usually  be  designated  by  a 
number  having  reference  to  some  standard  used  by  the  shop. 

Problem  1,  Plate  10.— Detail  of  a  Crosshead.  The  type  here  shown  differs  from  the  ordi- 
nary form  of  crosshead  in  being  made  in  halves,  the  parts  being  united  by  four  #)oIt8  which  also 
serve  to  clamp  the  piston-rod  to  the  crosshead,  and  to  prevent  any  movement  of  the  slide-gibs, 
other  than  tliat  governed  by  tiie  gib-screws.     Three  views   of  one-half  of  tlie  crosshead  will  be 


48  EXAMPLES    FOR    PRACTICE. 

required,  the  only  difference  between  the  halves  being  in  the  diameter  of  the  hole  for  the  crosshead- 
pin,  and  the  key  for  the  same.  A  note  will  suffice  to  ex[)lain  this  difference  and  if  thought  desir- 
able, one  of  these  holes  may  be  shown  in  red.  Two  views  of  the  slide-gib  will  be  sufficient.  The 
pin  and  screws  are  also  to  be  detailed.  The  scale  and  the  size,  number  and  arrangement  of  the 
sheets  are  left  to  the  discretion  of  the  student. 

Problem  8,  Plate  11.— Details  for  the  Head  Stock  of  a  17  Inch  Lathe.  The  section 
lines  clearly  indicate  the  character  of  the  metals  used,  and  the  drawing  and  figuring  is 
sufficiently  complete  to  enable  all  of  the  forms  and  dimensions  to  be  determined.  The  value  of  a 
carefully  made  lay-out  sketch  will  be  more  apparent  in  connection  with  this  problem  than  that  of 
any  preceding  one.  Draw  three  views  of  each  of  the  [larts  [upper  and  lower],  of  the  main  cast- 
ing. See  that  all  parts  are  completely  and  correctly  represented  and  figured,  that  the  number  of 
each  piece  and  the  cliaracter  of  the  metal  be  specified,  and  finally,  make  sure  of  the  accuracy  of 
all  by  a  careful  examination  of  every  detail  and  the  checking  of  the  figures. 

If  the  student  is  not  already  familiar  with  a  lathe,  he  should  inform  himself  concerning  its 
construction,  design  and  management,  by  such  means  as  he  may  have  at  his  command.  That 
most  to  be  desired  would  be  the  knowledge  gained  directly  from  the  working  machine  by  that  most 
valuable  of  all  educational  methods,  observation. 

Problem  9,  Plates  13,  13  ami  14.  (Also  see  Fig.  40.)  Assembled  Drawing  of 
the  Head  Stock  of  a  16  Inch  Lathe. — The  representation  required  is  that  shown  in  Fig.  40, 
save  that  it  must  be  more  complete,  involving  the  use  of  much  sectioning.  It  must  be  figured 
for  machinists  o«ly,  therefore  no  figures  for  finished  parts  must  be  omitted.  It  would  be  well  to 
draw  this  full-size  although  that  would  necessitate  a  very  large  sheet,  and  the  possible  separation 
of  the  front  and   side  views,  each   requiring  a  sheet.     The  sketches    have  been  drawn  to  no  scale, 


EXAMPLES    FOR    PRACTICE. 


49 


although  the  proportion  of  the  various  parts  have  been  preserved  where  practicable.  Small  parts 
have  necessarily  been  enlarged  in  order  to  make  the  drawing  legible.  Plate  12  includes  the  main 
casting  together  with  the  boxes  and  caps.     The  cone  and  coneheads  are   also  here  shown.     Plate 


FiC.  40 

13  illustrates  small  castings  and  brass  details  with  a  few  accompanying  forgings.  Plate  14  is 
devoted  to  forgings  and  gears.  By  reference  to  Fig.  40,  it  will  be  observed  that  in  the  main 
view,  the  upper  shaft,  called  the  quill,  is  a  revolved  position  of  that  shaft,  the  center  of  wliich  is 
shown  on  the  side  view  at  A.     If  an  attempt  had  been  made  to  draw  this  in  its  proper  position 


50  EXAMPLES    FOK   PRACTICE. 

beliind  the  main    casting,  it  would  have  resulted   in  confusion,  and  would   have  required  another 
view  to  illustrate  the   simple  details  shown  in  the  figure.     This  method  of    illustrating  a  train  of 
o-ears  as  though  their  shafts  were  all  in  one  plane  is  an  excellent  device  for  detailing  a  system  of 
^earino-,  showing  the  gears,  shafts,  distance  between  centers  and  the  actual  or   relative  velocity 
of  the  several  shafts.     In  connection  with  this,  an  end  view  should   be  shown  with  the  centers  of 
the  shafts  in   their  relative  positions  and   the  pitch  lines  of  the  gears  also  drawn.     AVhen  such  a 
representation  is  made  of  several  trains  of  mechanism  operated  by  a  single  driving  shaft,  but   per- 
forming different  functions,  the  pitch  lines  of  the  different  trains  may  to  advantage  be  represented 
in   different  colors.      Referring  again  to  Fig.  40,  it  will  be  seen  that  the  gears  shown  in  the  front 
view  are  shown  in    working  contact,  the   distance  between  their  centers  C   being  equal   to  one- 
half  the  sum  of  their  pitch  diameters.     But   in  the  side  view,  these  same  gears  are  not  drawn  in 
contact    but    in   their    extreme  position  to  the  left.     This  lateral  movement  of  the   back-gear  is 
accomplished  by  means  of  an  eccentric  quill  shaft,  as  may  be  seen  by  Plate  14.     The  intermediate 
o-ears  E  F  are  for  changing   the  direction  of  the   motion   transmitted  through  the  change   gear 
marked  K,  to  the  screw  operating   the   carriage  of  the  lathe,  but   not  shown  in  the  figure.     The 
centers  B  E  and  H  do  not  lie  in  the  same  plane,  and  since  it  would  be  desirable  to  represent  them 
in  the  same  sectional  plane,  when  drawing  the  front  view,  it  will  be  necessary  to  draw  the  shaft, 
havino-  its  center  at  H  at  a  different  hight  in  the  front  view  which  would  be   rather  objectionable, 
or  to  so  change  tlie  diameters  of  gears  E  and  H  that  the   gear  E  could   be  shown   in  the  plane  of 
the  other  two.     The  error  in  the  drawing  made  by  using  this  latter  method,  which  is  the  better  of 
the  two,  will  not  be  perceptible.     The  figures  for  the  pitch  diameter  would  of  course  be  figured 

correctly. 

As   in   the   preceding  problem,  this  study  should   be  anticipated  by  first  gaining  a  thorough 

knowledge  of  the  lathe  and  its  operation. 


Plate  1. 


Plate  1 


1—  -^i       -H 


7%3.  3  /S93 


Plate  2. 


Plate  2 


^^ 


»^^^ 


r-^~-,Sf. 


.Mk. 


L    m 


-v-^-" 


/:^[Sro7^ze  CA&ci^l^&e., 


Plate  3. 


Plate  3 


'/Globe  i/alve 
lie  full  Size 
•  1 2.  /89S 


Plate  4. 


Plate  4 


Fig.  4 


Plate  5. 


Plate  5 


CONNECTING  ROD  END. 
SCALE  FULL  SIZE. 
SEPT   6  1833 


Plate  6. 


Plates 


Ju/if26  /893 


Plate  7. 


PtATE? 


TWO  8E/*RIN(>   NUTS.  one;  DRIVING- PULLEY.      OI^E  LOOSE  PuLlEY. 


^  iSCREW    POLISHING 

MACHINE. 

J        iC AST  IRON  DETAILS, 

+f H  SCALE  FULL  SIZE. 

AUG.I2.I893 


Plate  8. 


Plates 


one:  tail  scrcw 


OME   REAR  BEARING. 


ONE    e'SonT   bearing. 


—  Z^i 


r^6-  -  ,r 


^^f^ 


ONEWASHEB  TWO   CAPS  OME  N'UT  SCREW.  ONE    CENTCR  DRIVE  ONECENTER 

ONESPRIN&  Nol7WIRE.  ONE  ORIVIiM&PULLfy      ONE    LOOSE   PuulEy 


^ri 


^*- 


SCHEW. 


T 


HAADEN  %    GRIND 


16  ,U.^p 


"^ 


1 


SCREW. 


T I  ri 


1^- 


jL 


^     -t 


a  DCN  C-    GPi  N  O 


ONE    SPINDLE. 


SCREW  POLISHINGMACHINE 
STEEL  FORGING  DETAILS. 
SCALE    FULL  SIZE 
AUG  12.1893 


Plate  9. 


Plate  9 


"vt 


J L 


-rt 


^^ 


11. 


ijjj 


-  -w 


^ 


r  r- 


±1 


K^- 


Sco\e  ".  ^\x\\.  S\.xe. 


Plate  10. 


Plate  10 


Cross/iecj 
rSco/e  :  3fnc/ieS'=J/oot. 


Plate  11 


Plate  11. 


Plate  1 1 


Sact^vo  n  <7tt  C,3: 


17"XJatfic. 
OaltSiock. 

Oc\.2.\&90, 


Plate  12. 


Plate.  1  2 


Co^G  —  Ca.^t  Iron. 


^'^T^ 


//ecc*/ —  Oust  -/V<??7 


^e.a</ StocAr  JDeMfU  Se^^^ sS^/8^^ 


Plate  13. 


Plate.  13 


r/6li 


Plate  14. 


Plate  1  4 


-.£s^lLXr ^'f ■  ^p^-'^J^'^-^ct9t-:o...  ^ ^^r"  ^'^^J/%  ^^""^s.fef.'^  .r-/,<"'*— s)s^t.'M 


^//////.'///y/.y. 


/'/     >»«      /•  ■ ,.  <  .rig  .  /^-a 


wmmm :    in 


St^&Z 


Spin.uZe.Qeo.^  Cast  Iro-rv 


^  £  3       > 

Quill  Qear.  ~  'Cast  7,x>ri 


Q-Lc^Zl—C'cLSi  jTon, 


^&ci/^  SCocA:J)e£a,ils. 
Se^^  JB^''  ■.■rf3. 


zLocZ  /Vt^C-S^e^T 


Plate  15. 


Plate  15 


FlG.1 


Fig.  2 


Fig.  3 


Fig.  4 


''/ 

'//////V///// 

Fig.  5 


Fig  6 


Fig.  7 


Fig.  8 


VISIBLE    LINE 

y/  /  /j  "  "  ^  '//^ '/ 

VISIBLE    LINE  [SHADED] 

INVISIBLE     LINE 

CENTER    LINE 

IMAD-INflRY  LINE 

FIGURE    LINE 

-> 

Fig.  9 


Fig.1  1 


Fig.  10 


Plate  16. 


Plate  16 


FiG.2 


Fig.  3 


FlQ.1 


W 

— 1 

W 

m 

FiG.4 


Fig.  5 


Fig.  9 


'I 


o 
o 


(A 

o 

c 

<  5  >2. 

CT  O    00  = 
O   -»  3)  o 

(0    CT  _ 

p-s  5 


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A     000  019  600     6 


Univers 

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Lib 


